Celestron 93517 Instruction manual

C150-HD AND G-8N NEWTONIAN

INSTRUCTION MANUAL

Models #31056 and #31058

T A B L E O F C O N T E N T S

How to Use This Manual ................................................................................................................................ 6

A Word of Caution .......................................................................................................................................... 6

The Newtonian Optical System ...................................................................................................................... 7

Unpacking Your Telescope ............................................................................................................................ 8

Setting Up the Tripod ................................................................................................................................... 11

Adjusting the Tripod Height ........................................................................................................................ 11

Attaching the Accessory Tray ....................................................................................................................... 12

Attaching the Equatorial Mount .................................................................................................................. 13

Attaching the R.A. Slow Motion Knob .......................................................................................... 14

Attaching the Declination Slow Motion Knob .............................................................................. 15

Installing the Counterweight Bar & Counterweights .................................................................... 16

Attaching the Telescope to the Mount ......................................................................................................... 17

Balancing the Telescope in R.A. .................................................................................................... 19

Balancing the Telescope in DEC ................................................................................................... 20

Adjusting the Mount in Altitude .................................................................................................................. 21

Adjusting the Mount in Azimuth ................................................................................................................. 21

Disassembling and Transporting Your G-8N ................................................................................................ 22

Storing Your Telescope ................................................................................................................................ 22

Installing the Finderscope ............................................................................................................................ 23

Installing the Eyepiece ................................................................................................................................. 24

Technical Specifications .............................................................................................................................. 25

Image Orientation ......................................................................................................................................... 26

Focusing ........................................................................................................................................................ 27

Aligning the Finder ....................................................................................................................................... 28

Your First Look ............................................................................................................................................. 29

Daytime Observing ......................................................................................................................... 29

Nighttime Observing ...................................................................................................................... 30

Calculating Magnification (Power) .............................................................................................................. 31

Determining the Field of View ..................................................................................................................... 31

The Celestial Coordinate System ................................................................................................................. 32

Motion of the Stars ....................................................................................................................................... 33

Polar Alignment ............................................................................................................................................ 34

Finding the Pole ............................................................................................................................................ 35

Latitude Scales .............................................................................................................................................. 36

Pointing at Polaris ......................................................................................................................................... 37

Declination Drift ........................................................................................................................................... 38

Polar Axis Finder .......................................................................................................................................... 39

Aligning the R.A. Setting Circle .................................................................................................................. 39

Table of Contents • i

Observing the Moon ..................................................................................................................................... 40

Observing the Planets ................................................................................................................................... 40

Observing the Sun ......................................................................................................................................... 41

Observing Deep-Sky Objects ........................................................................................................................ 41

Using the Setting Circles ................................................................................................................ 42

Star Hopping ................................................................................................................................... 43

Viewing Conditions ...................................................................................................................................... 45

Transparency .................................................................................................................................. 45

Sky Illumination ............................................................................................................................. 45

Seeing ............................................................................................................................................. 45

Short Exposure Prime Focus ......................................................................................................................... 48

Piggyback ..................................................................................................................................................... 49

Care and Cleaning of the Optics ................................................................................................................... 51

Collimation ................................................................................................................................................... 51 ii • Table of Contents

I N T R O D U C T I O N

Welcome to the Celestron world of amateur astronomy! Celestron has been providing amateur astronomers with the tools to explore the universe for more than a quarter of a century. The Celestron Newtonian telescope continues in this proud tradition. With a mirror diameter of 6", your C150-HD has almost 500 times the light gathering power of the unaided human eye. The G-8N, with its 8" diameter mirror gathers almost 800 times the light of your eye. It can show you literally thousands of deep-sky objects. Yet your Celestron Newtonian telescope is compact enough to take to the mountains or desert or wherever you observe.

This telescope is made of the highest quality materials to ensure durability and stability. All this adds up to a telescope that gives you a lifetime of pleasure with a minimal amount of maintenance. And, your Celestron telescope is versatile. It grows as your interest grows. All you need to do is take the time to familiarize yourself with your telescope and its operation.

Introduction • 5

How to Use this Manual

This manual is designed to instruct you in the proper use of your Celestron

Newtonian telescope. The instructions are for assembly, initial use, long term operation, and maintenance. There are seven major sections to the manual. The first section covers the proper procedure for setting up your Celestron telescope. This includes setting up the tripod, attaching the telescope to the mount, balancing the telescope, etc.

The second section deals with the basics of telescope use. Topics include focusing, aligning the finder, and taking your first look. The third section deals with the basics of astronomy which includes the celestial coordinate system, the motions of the stars, and polar alignment. The fourth section deals with celestial observing covering visual observations of the planets and deep-sky objects. Using both the setting circles and star hopping are discussed. The fifth section covers celestial photography working from the easiest to the most difficult. The last major section is on telescope maintenance, specifically on cleaning and collimation. Keeping your telescope in proper collimation is the single most important thing you can do to ensure it performs well.

In addition to the major sections mentioned previously, there is a list of optional accessories for your telescope that include a brief description of its purpose. This is the section to consult when you’ve mastered the basics and ready for new, more challenging observations. The final part of this manual contains a list of objects that can be observed through your Celestron telescope. Included are the coordinates for each object, its brightness, and a code which indicates what type of an object it is. In addition, there is a list of bright stars used for aligning the setting circles.

Read the assembly instructions through completely before you attempt to set up your telescope. Then, once you’ve set up your telescope, read the section on

“Telescope Basics” before you take it outside and use it. This will ensure that you are familiar with your telescope before you try to use it under a dark sky. Since it will take a few observing sessions to familiarize yourself with your telescope, you should keep this manual handy until you have fully mastered your telescope’s operation. After that, save the manual for future reference.

A Word of Caution!

WARNING !

Your Celestron telescope is designed to give you hours of fun and rewarding observations. However, there are a few things to consider before using your telescope that will ensure your safety and protect your eyes and your equipment.

NEVER LOOK DIRECTLY AT THE SUN WITH THE NAKED EYE

OR WITH A TELESCOPE. NEVER POINT YOUR TELESCOPE AT

THE SUN UNLESS YOU HAVE THE PROPER SOLAR FILTER.

PERMANENT AND IRREVERSIBLE EYE DAMAGE MAY RE-

SULT AS WELL AS DAMAGE TO YOUR TELESCOPE.

NEVER USE YOUR TELESCOPE TO PROJECT AN IMAGE OF

THE SUN ONTO ANY SURFACE. INTERNAL HEAT BUILD-UP

CAN DAMAGE ANY ACCESSORIES ATTACHED TO THE TELE-

SCOPE.

NEVER LEAVE THE TELESCOPE UNSUPERVISED, ESPECIALLY WHEN

CHILDREN ARE PRESENT OR OTHER ADULTS WHO MAY NOT BE

6 • Introduction

The Newtonian

Optical System

FAMILIAR WITH THE CORRECT OPERATING PROCEDURES OF YOUR

TELESCOPE.

NEVER USE AN EYEPIECE SOLAR FILTER OR A HERSCHEL

WEDGE SOLAR FILTER. INTERNAL HEAT BUILD-UP INSIDE

THE TELESCOPE CAN CAUSE THESE DEVICES TO CRACK OR

BREAK.

NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS USING

THE PROPER SOLAR FILTER. WHEN USING A SOLAR FILTER,

ALWAYS COVER THE FINDER. ALTHOUGH SMALL IN APER-

TURE, THE FINDER HAS ENOUGH LIGHT GATHERING

POWER TO POSSIBLY CAUSE PERMANENT AND IRREVERS-

IBLE EYE DAMAGE. THE IMAGE PROJECTED BY THE

FINDER IS HOT ENOUGH TO BURN SKIN OR CLOTHING.

The Newtonian reflector was developed by Isaac Newton in the late 1600’s and therefore carries his name. This type of telescope uses a primary mirror to focus the light rays it collects. In addition to focusing the light, the mirror also redirects them toward the front of the telescope tube where the light entered. Near the front of the tube, the light rays are intercepted by a small flat secondary mirror (sometimes called an elliptical flat) and directed out of the telescope tube at a 90° angle to the incoming light rays (see figure 1-1). It is here that the eyepiece is placed to view the image formed by the telescope. Because mirrors, not lenses, are used, much larger light gathering areas can be used without fear of gravity distorting them. Furthermore, these larger aperture systems become much more portable that comparable refractors.

Figure 1-1

This cross sectional diagram shows the light path of the Newtonian optical system. All optical elements are labeled.

Introduction • 7

A S S E M B L I N G Y O U R N E W T O N I A N T E L E S C O P E

This section covers the proper assembly instructions for your G-8N and C150-HD reflecting telescope. These telescopes are Newtonian reflector that utilize mirrors with specific focal lengths. The telescope comes on the German equatorial mount, which when properly aligned and fitted with the optional motors, will track objects as they move across the sky. Each telescope contains the following standard accessories. Included are:

• 20mm Eyepiece 1-1/4"

• 6x30mm Finder (Model #31056)

• 9x50mm Finder (Model #31058)

• Quick Release Finder Bracket

• Lens Cap

• CG-4 German Equatorial Mount (Model #31056)

• CG-5 German Equatorial Mount (Model #31058)

• Counterweight Bar

• Counterweight (5 kg for Model #31058 - 3.6kg and 1.8kg for Model #31056)

• Declination (DEC) Slow Motion Knob

• Right Ascension (R.A.) Slow Motion Knob

• Adjustable Aluminium Tripod

• Accessory Tray

Unpacking Your

G - 8 N

When setting up the telescope, find a large, clear area where the parts can be laid out without fear of losing them. Start with the tripod and mount. Remove the contents of the box and place them neatly on your work surface. Leave the optical tube in its box until you are ready to attach it to the mount. Once your telescope has been unpacked and assembled, you will not need the shipping boxes for everyday storage and transportation. However, you should save them in case you decide to ship your telescope via a common carrier.

8 • The C150-HD

10

9

15

14

13

12

The G-8N

8

7

5

6

1

2

3

4

1. Finderscope

2. Finderscope Bracket

3. Tube Ring

4. Piggyback Adapter

5. Latitude Scale

6. Latitude Adjustment Screw

7. Tripod

8. Accessory Tray

Figure 2-1

G-8N with CG-5 Equatorial Mount

9. Tripod Leg Clamp

10. Leg Brace Assembly

11. Counterweight

12. Counterweight Shaft

13. Equatorial Mount

14. Focuser

15. Eyepiece

The G-8N • 9

The C150-HD

15

14

13

12

11

10

9

1. FinderscopeBracket

2. Finderscope

3. Tube Ring

4. Primary Mirror (inside tube)

5. Solw Motion Cables

6. Latitude Scale

7. Latitude Adjustment Screw

8. Tripod

Figure 2-1A

C150-HD with CG-4 Equatorial Mount

9. Accessory Tray

10. Counterweight

11. Counterweight Shaft

12. Declination Circle

13. Mounting Platform

14. Eyepiece

15. Secondary Mirror

10 • The C150-HD

1

2

3

4

5

6

7

8

Assembling the Equatorial Mount

Setting Up the Tripod

The tripod comes fully assembled with the metal plate, called the tripod head, that holds the legs together at the top. In addition, the brackets that support the accessory tray are also attached to the tripod.

Stand the tripod upright and pull the tripod legs apart until the leg brace assembly for the accessory tray is fully extended (see figure 2-2). The tripod will now stand by itself. To increase the stability, tighten the bolts that hold the legs to the tripod head (use the appropriate size wrench from the supplied set). This will help minimize any flexure or wobble of the legs.

Adjusting the Tripod

Height

Once the tripod is set up, you can adjust the height at which it stands. To do this:

1.

Loosen the knob on the leg clamp so that the tripod leg can be adjusted.

2.

Slide the center portion of the tripod leg away from the tripod head until it is at the desired height.

3.

Tighten the knobs on each leg clamp to hold the legs in place.

With the tripod set up, you are ready to attach the accessory tray to the tripod.

Figure 2-2

Setting up the tripod requires nothing more than pulling the tripod legs away from the tripod head. The height at which the tripod stands can be adjusted by sliding the slats in the center of each leg toward or away from the tripod head.

The G-8N • 11

Attaching the Accessory

Tray

There are three wing bolts that hold the accessory tray to the center leg brace.

1.

Locate the three wing bolts.

2.

Place the accessory tray over the leg brace and position it so the thread holes in the accessory tray are above the slotted holes in the bracket.

3.

Insert the wing bolts up through the slotted holes in the leg brace (see figure 2-

3).

4.

Thread the wing bolts into the holes in the accessory tray.

5.

Tighten the wing bolts fully.

With the accessory tray in place, the tripod will be much more stable making it easier to attach the mount and telescope.

Figure 2-3

12 • The C150-HD

Attaching the Equatorial

Mount

The equatorial mount allows you to tilt the telescope’s axis of rotation so that you can track the stars as they move across the sky. The CG-4 and CG-5 mounts are

German equatorial mounts that attache to the tripod head (i.e., metal plate on the tripod). On one side of the plate there is an “N” which signifies north. This side of the tripod will face north when setting up for an astronomical observing session.

Above the “N” is a peg about 3/4" high that points straight up. To attach the equatorial head:

1.

Locate the azimuth adjustment screws on the equatorial mount.

2.

Retract the screws so they no longer extend into the azimuth housing

(rectangular extrusion) on the mount. Do NOT remove the screws since they are needed later for polar alignment.

3.

Hold the equatorial mount over the tripod head so that the azimuth housing is above the metal peg.

4.

Place the equatorial mount on the tripod head so that the two are flush.

5.

Tighten the knob on the underside of the tripod head to hold the equatorial mount firmly in place. The knob is already attached and can NOT be removed.

Figure 2-4

The G-8N • 13

14 • The C150-HD

Attaching the R.A. Slow Motion Knob

With the mount securely in place, you are ready to attach some of the accessories

(the telescope tube will be added last). Start with the Right Ascension (R.A.) slow motion knob. The R.A. slow motion knob allows you to make fine pointing adjustments in the direction the telescope is aiming (once it is attached to the mount). To install the knob:

1.

Locate the hard plastic shell under the R.A. shafts.

2.

Remove either of the two oval tabs by pulling tightly.

3.

Line up the flat area on the inner portion of the R.A. slow motion knob with the flat area on the R.A. shaft..

4.

Slide the R.A. slow motion knob onto the R.A. shaft.

The knob is a tension fit, so sliding it on holds it in place. As mentioned above, there are two R.A. shafts, one on either side of the mount. It makes no difference which shaft you use since both work the same. Use whichever one you find more convenient. If, after a few observing sessions, you find the R.A.

slow motion knob is more accessible from the other side, pull firmly to remove the knob, then install it on the opposite side.

Mounting Platform

Mounting Platform

Safety Screw

DEC Slow Motion

Knob

R.A. Setting

C i r c l e

Polar Housing

Cover

Altitude Adjustment

Control

Telescope

Mounting Screw

DEC Lock

Lever

RA Lock

Lever

Declination Setting

C i r c l e

R.A. Slow Motion

Knob

Azimuth Adjustment

Controls

Figure 2-5

The CG-5 Equatorial Mount

Attaching the Declination Slow Motion Knob

Like the R.A. slow motion knob, the DEC slow motion knob allows you to make fine pointing adjustments in the direction the telescope is pointed.

The DEC slow motion knob attaches in the same manner as the R.A. knob. The shaft that the DEC slow motion knob fits over is toward the top of the mount, just below the telescope mounting platform. Once again, you have two shafts to choose from.

Use the shaft that is pointing toward the ground. This makes it easy to reach while looking through the telescope, something which is quite important when you are observing.

1.

Line up the flat area on the inner portion of the DEC slow motion knob with the flat area on the DEC shaft.

2.

Slide the DEC slow motion knob over the DEC shaft (see figure 2-6).

Figure 2-6

The G-8N • 15

Attaching the Counterweight Bar and Counterweight

The last item to be mounted before the telescope tube is the counterweight bar and counterweight. Used to balanced the telescope, the counterweight bar attaches to the opposite side of the mount as the telescope. To install the counterweight bar:

1.

Retract the counterweight bar lock nut by turning it counterclockwise. This will expose the threads on the end of the counterweight bar.

2.

Thread the counterweight bar into the mount completely. Once again, it

threads into the mount opposite the telescope (see figure 2-7).

3.

Tighten the counterweight bar lock nut fully for added support.

The counterweight bar is now installed. With the counterweight bar in place, you are ready to attach the counterweight.

1.

Lock the DEC clamp to hold the mount in place.

2.

Remove the safety thumbscrew on the end of the counterweight bar.

3.

Loosen the set screw on the counterweight itself so that the central hole of the counterweight is unobstructed.

4.

Slide the counterweight onto the counterweight bar (see figure 2-7).

5.

Tighten the set screw on the counterweight to hold it in position.

6.

Replace the safety thumbscrew on the end of the counterweight bar. The thumbscrew will prevent the counterweight from sliding off the bar should they ever become loose.

With the mount fully assembled, you are ready to attach the telescope to the mount.

16 • The C150-HD

Counterweight Bar

Lock Nut

Counterweight Bar

C o u n t e r w e i g h t

Counterweight Lock

S c r e w

C o u n t e r w e i g h t

Safety Screw

Figure 2-7

Attaching the Telescope to the Mount (For G-8N)

NOTE:

Before you attach the optical tube, fully tighten the right ascension and declination clamps. This will prevent the telescope from moving suddenly once attached to the mount.

1 Locate the mounting bracket from the box containing the equatorial mount head.

2 Attach the mounting bracket to the tube rings so that the tappered (narrow) end is against the bottom of the tube rings.

3 Loosen the hand knob on the side of the CG-5 mount.

4 Slide the mounting bracket that is attached to the bottom of the tube rings into the reccess on the top of the mounting platform (see figure 2-8).

5 Tighten the telescope mounting screw on the CG-5 mount to hold the telescope in place.

6 Hand tighten the mounting platform safety screw until the tip touches the side of the mounting bracket (see figure 2-5).

Never loosen any of the knobs on the telescope tube or mount. Also, be sure that the open end of the telescope is pointing away from the ground at all times.

Tube Rings

Mounting Bracket

Mounting Platform

Telescope Mounting

S c r e w

Figure 2-8

This illustration shows the correct mounting procedure for the optical tube onto the CG-5 mount. The mounting bracket has been attached to the telescope tube rings and is ready to attach to the CG-5 mount.

The G-8N • 17

Attaching the Telescope to the Mount (For C150-

HD)

Before you attach the optical tube, make sure that the declination and right ascension clamps are tight. The optical tube attaches to the mount via two rings that are mounted on the tube of the telescope. To mount the telescope tube:

1. Loosen the knobs on the side of the rings. This will allow you to slide the mounting rings the length of the optical tube.

2. Locate the two holes on either end of the CG-4 mounting platform.

3. Hold the telescope up to the mount and slide the mounting rings until they are over the holes on the mounting platform.

4. Place the flat portion of the ring over the mount so that the hole in the ring is over the holes of the mounting platform.

5. Thread the mounting screws underneath the mounting platform to secure the rings.

Tighten the knobs on the side of the mounting rings to prevent the telescope from sliding forward or backward. These can be loosened later to reposition the telescope during the balancing process.

Tube Rings

Mounting Platform

18 • The C150-HD

Figure 2-8A

This illustration shows the correct mounting procedure for the C150-HD optical tube onto the CG-4 mount.

Removing the Lens

C a p

The G-8N lens cover has a 1-1/2" cap covering an aperture stop that is offset from the center. To utilize the aperture stop, leave the telescope cover on the front of the tube and remove only the small aperture stop cap from the front of the cover. This is useful when observing very bright objects, like the full moon. The aperture stop reduces the amount of light entering the tube resulting in better resolution. Do not use the aperture stop to view the Sun unless using a proper solar filter.

Balancing the Telescope in R.A.

To eliminate undue stress on the mount, the telescope should be properly balanced around the polar axis. In addition, proper balancing is crucial for accurate tracking if using an optional motor drive. To balance the mount:

1.

Release the R.A. Clamp and position the telescope off to one side of the mount (make sure that the mounting bracket screw is tight). The counterweight bar will extend horizontally on the opposite side of the mount (see figure 2-9).

2.

Release the telescope — GRADUALLY — to see which way the telescope

“rolls.”

3.

Loosen the set screw on the counterweight.

4.

Move the counterweight to a point where it balances the telescope (i.e., it remains stationary when the R.A. clamp is released).

5.

Tighten the set screw to hold the counterweight(s) in place.

These are general balance instructions and will reduce undue stress on the mount. When taking astrophotographs, this balance process should be done for the specific area at which the telescope is pointing.

Figure 2-9

The telescope should be balanced after all the standard accessories (i.e., finderscope, eyepiece, etc.) have been attached to the telescope. The correct procedure for attaching these accessories is discussed latr in this section.

The G-8N • 19

Balancing the Telescope in DEC

The telescope should also be balanced on the declination axis to prevent any sudden motions when the DEC clamp is released. To balance the telescope in

DEC:

1.

Release the R.A. clamp and rotate the telescope so that it is on one side of the mount (i.e., as described in the previous section on balancing the telescope in R.A.).

2.

Lock the R.A. clamp to hold the telescope in place.

3.

Release the DEC clamp and rotate the telescope until the tube is parallel to the ground (see figure 2-10).

4.

Release the tube — GRADUALLY — to see which way it rotates around the declination axis. DO NOT LET GO OF THE TELESCOPE TUBE

COMPLETELY!

5.

Loosen the screws that hold the telescope tube inside the mounting rings and slide the telescope either forwards or backwards until it remains stationary when the DEC clamp is released.

6.

Tighten the tude ring screws firmly to hold the telescope in place.

Like the R.A. balance, these are general balance instructions and will reduce undue stress on the mount. When taking astrophotographs, this balance process should be done for the specific area at which the telescope is pointing.

20 • The C150-HD

Figure 2-10

As with R.A., the telescope should be balanced in DEC after all the standard accessories

(i.e., finderscope, eyepiece, etc.) have been attached to the telescope.

Adjusting the Mount in Altitude

For the purpose of polar alignment, there are two directions in which the mount can be adjusted; vertically, which is called altitude and horizontally, which is called azimuth. There are several ways to align on the celestial pole, many of which are discussed later in this manual. This section simply covers the correct movement of the mount during the polar alignment process. To adjust the mount in altitude (i.e., raise or lower the angle of the polar axis), turn the altitude adjustment screw:

• Turning the knob clockwise increases the angle at which the polar axis is pointing

• Turning the handle counterclockwise lowers the angle at which the polar axis is pointing.

The latitude adjustment on the CG-4 and CG-5 mount has a range of 40°, starting at

20° going up to 60°.

Adjusting the Mount in Azimuth

For rough adjustments in azimuth, simply pick up the telescope and tripod and move it. For fine adjustments in azimuth:

1.

Turn the azimuth adjustment screws located on either side of the azimuth housing at the base of the mount. While standing behind the telescope, the knobs are on the front of the mount.

• Turning the right adjustment knob clockwise moves the mount toward the right.

• Turning the left adjustment knob clockwise moves the mount to the left.

Both screws push off of the peg on the tripod head, which means you may have to loosen one screw while tightening the other. The screw that holds the equatorial mount to the tripod may have to be loosened slightly.

Figure 2-11

The G-8N • 21

Disassembling and

Transporting Your

Telescope

The entire telescope and mount is light enough to pick up and carry outside for a casual observing session. If, however, you want to transport your telescope to a remote observing location, you must partially disassemble it. Here’s how:

1.

Remove the telescope from the equatorial mount. Return it to the shipping carton to ensure safe transportation.

2.

Remove the three wing bolts that hold the accessory tray to the tripod.

3.

Pull the accessory tray off the bracket.

4.

Thread the wing bolts back onto the accessory tray once they are removed from the bracket. This will eliminate the possibility of losing them.

5.

Fold the tripod legs together and you are ready to transport your telescope.

The equatorial mount does NOT have to be removed if you are transporting the telescope yourself. However, you may want to remove the counterweight from the counterweight bar to lighten the mount.

If you are shipping the telescope via a common carrier, you should completely disassemble the telescope and return all parts to their original shipping container.

Storing Your Telescope

When not in use, your Celestron telescope can be left fully assembled and set up.

However, all lens and eyepiece covers should be put back in place. The opening to the focuser must also be covered. This will reduce the amount of dust build-up on the optical surfaces and reduce the number of times you need to clean the instrument. You may want to return everything to its original shipping container and store all the parts there. If this is the case, all optical surfaces should still be covered to prevent dust build-up.

Now that you have completed assembling your telescope, you are ready to begin attaching the accessories.

22 • The C150-HD

Installing the

F i n d e r s c o p e

4.

5.

6.

1.

To install the finderscope onto the telescope you must first mount the finderscope through the finder bracket and then attach it to the telescope. Toward the front of the telescope tube, near the focusing assembly, there is a small bracket with a set screw in it. This is where the finderscope bracket will be mounted. To install the finderscope:

2.

Slide the rubber O-ring over the eyepiece end of the finderscope and roll it 2/3 of the way up the finderscope.

Insert the eyepiece end of the finderscope through the bracket until the

O-ring presses tightly between the finder and the inside of the bracket.

3.

Tighten the adjustment screws until they make contact with the finderscope body.

Locate the mounting bracket near the front (open) end of the telescope.

Loosen the set screw on the mounting bracket on the telescope.

7.

8.

Slide the finder bracket (attached to the finderscope) into the mounting bracket on the telescope.

The finderscope bracket will slide in from the back. The finderscope should be oriented so that the objective lens is toward the front (open) end of the telescope (see figure 2-12).

Tighten the set screw on the mounting bracket to hold the finderscope in place.

Figure 2-12

The G-8N • 23

Installing the Eyep i e c e

The eyepiece, or ocular as it is also called, is an optical element that magnifies the image focused by the telescope. Without the eyepiece it would be impossible to use the telescope visually. The eyepiece fits directly into the eyepiece holder. To attach an ocular:

1.

Loosen the set screw on the eyepiece holder so that it does not obstruct the inner diameter of the eyepiece holder.

2.

Slide the chrome portion of the eyepiece into the eyepiece holder.

3.

Tighten the set screw to hold the eyepiece in place.

To remove the eyepiece, loosen the set screw on the eyepiece holder and slide the eyepiece out. You can replace it with another ocular.

Eyepieces are commonly referred to by focal length which is printed on the eyepiece barrel. The longer the focal length (i.e., the larger the number) the lower the eyepiece power and the shorter the focal length (i.e., the smaller the number) the higher the magnification. Generally, you will use low-to-moderate power when viewing. For more information on how to determine power, see the section on “Calculating Magnification.”

In addition, eyepieces are also referred to by barrel diameter. The C150-HD and G-

8N use eyepieces with a barrel diameter of 1-1/4".

Once the telescope is fully assembled, tighten the bolts that hold the tripod legs to the tripod head and the bolts that adjust the tripod height. Check these bolts periodically to ensure they are tight. The first check should be done 24 hours after initial assembly.

24 • The C150-HD

Figure 2-13

Technical

Specifications

Below is pertinent technical information on your G-8N and C150-HD telescope that you may find useful.

Optical System:

Aperture:

G-8N

Newtonian Reflector

200mm (8")

C150-HD

Newtonian Reflector

150mm (6")

Focal Length: 1000mm (40") 750mm (30")

Highest Useful Power:

Resolution (arc seconds):

480x

0.58

Light Gathering Power: 816

Limiting Visual Magnitude: 14

360x

.77

459

13.5

Secondary Obstruction

% of Primary Surface Area

2.9"

13.1%

2.2"

13.4% f/ratio: f/5 f/5

Length: 19.75" 14.5"

Weight

Optical Tube: 15.5 lb. 8.5 lb.

With Tripod: 30.5 lb. 25lb.

These specifications are approximate and subject to change without notice.

The G-8N • 25

T E L E S C O P E B A S I C S

Image Orientation

Once your telescope has been fully assembled and the accessories attached, you are ready to take a look. This section deals with basic telescope operation.

The Newtonian optical system produces an upside down image. This will only affect your terrestrial observations. For celestial viewing, star charts can be made to match the view in the telescope by rotating the chart 180° about the center. The view through the finder is also inverted.

Actual Veiw

Newtonian View

Figure 3-1

The figure illustrate the image orientation of a Newtonian telescope. Top is the actual orientation while below is the image seen through the telescope. The finderscope produces an inverted (upside-down and backwards)image.

26 • Telescope Basic

Focusing

To focus your telescope, simply turn the focus knob located directly below the eyepiece holder (see figure 2-13). Turning the knob clockwise allows you to focus on an object that is farther than the one you are currently observing.

Turning the knob counterclockwise from you allows you to focus on an object closer than the one you are currently observing.

In addition to understanding how the focusing mechanism works, there are a few focusing hints that should be remembered when using any optical instrument.

• Never look through glass. Glass found in household windows is optically imperfect, and as a result, may vary in thickness from one location to the next. This inconsistency can and will affect the ability to focus your telescope. In most cases you will not be able to achieve a truly sharp focus.

In some cases, you may actually see a double image.

• Never look across or over objects that are producing heat waves. This includes asphalt parking lots on hot summer days or building roof tops.

• Hazy skies, fog and mist can also make it difficult to focus. The amount of detail that can be seen under these conditions will be greatly reduced.

• When using your telescope as a telephoto lens, the split screen focuser of the 35mm camera may “black out.” This is common with all long focal length lenses. If this does happen, use the ground glass portion of your focusing screen. To achieve a very sharp focus, consider using a focusing magnifier which is readily available from your local camera store.

• If you wear corrective lenses (specifically glasses), you may want to remove them when observing with an eyepiece attached to the telescope. However, when using a camera you should always wear corrective lenses to ensure the sharpest possible focus. If you have astigmatism, corrective lenses must be worn at all times.

Telescope Basics • 27

Aligning the Finder

Accurate alignment of the finder makes it easy to find objects with the telescope, especially celestial objects. To make aligning the finder as easy as possible, this procedure should be done in the daytime when it is easy to find and identify objects.

The finderscope has a spring-loaded adjustment screw that puts pressure on the finderscope while the remaining screws are used to adjust the finder horizontally and vertically. To align the finder:

1 Choose a target that is in excess of one mile away. This eliminates any possible parallax effect between the telescope and finder.

2 Release the R.A. and DEC clamps and point the telescope at your target.

3 Center your target in the main optics of the telescope. You may have to move the telescope slightly to center it.

4 Adjust the screw on the finder bracket that is on the right (when looking through the finder) until the cross hairs are centered horizontally on the target seen through the telescope.

5 Adjust the screw on the top of the finder bracket until the cross hairs are centered vertically on the target seen through the telescope.

Image orientation through the finder is inverted (i.e., upside down and backwards left-to-right). This is normal for any finder that is used straight-through.

Because of this, it may take a few minutes to familiarize yourself with the directional change each screw makes on the finder.

28 • Telescope Basic

Your First Look

WARNING !

With the telescope fully assembled and all the accessories attached you are ready for your first look. Your first look should be done in the daytime when it is easier to locate the locking clamps and slow motion adjustment knobs. This will help to familiarize you with your telescope, thus making it easier to use at night.

Daytime Observing

1.

Begin by finding a distant object that is fairly bright.

2.

Insert a low power eyepiece (one with a large focal length) into the telescope.

3.

Release the R.A. and DEC clamps and point the telescope at the object you selected.

4.

Locate the object in your finder and lock the R.A. and DEC clamps.

5.

Use the slow motion knobs to center the object in the field of the finder.

6.

Once centered, look through your telescope and the object will be there (if you aligned the finder first).

Try using different optional eyepieces to see how the field changes with various magnifications.

NEVER POINT YOUR TELESCOPE AT THE SUN UNLESS YOU

HAVE THE PROPER SOLAR FILTER. PERMANENT AND IRRE-

VERSIBLE EYE DAMAGE MAY RESULT AS WELL AS DAMAGE TO

YOUR TELESCOPE. ALSO, NEVER LEAVE YOUR TELESCOPE

UNATTENDED DURING A DAYTIME OBSERVING SESSION, ESPE-

CIALLY WHEN CHILDREN ARE PRESENT.

Telescope Basics • 29

30 • Telescope Basic

Nighttime Observing

Looking at objects in the sky is quite different than looking at objects on Earth.

For one, many objects seen in the daytime are easy to see with the naked eye and can be located by using landmarks. In addition, objects on the ground are stationary, or at least for the most part. In the night sky you will see a tremendous amount of stars that are not visible to the naked eye and the only way to find objects (at least initially) is by using other stars to guide you there. This method of finding objects, known as star hopping, is very accurate. Yet it requires a fair amount of time to learn the stars well enough so as to guide you to other objects. Furthermore, the stars appear to drift out of the field of view.

This is due to the Earth’s rotation. In fact, anything in the sky, day or night, will drift out unless the telescope has been polar aligned and the optional clock drive is running. There is more on this in the section on “Polar Alignment.”

1.

Orient the telescope so that the R.A. or polar axis is pointing north, as close to true north as possible. You can use a landmark that you know faces north to get you in the general direction.

2.

Adjust the mount until the latitude indicator points to the latitude from which you are observing.

3.

Insert an eyepiece into the telescope. It should be a low power eyepiece

(i.e., one with a large number on the side) to give you the widest field possible.

4.

Turn the motor drive on (if you are using one).

5.

Release the right ascension and declination clamps and point the telescope at the desired target. The Moon or one of the brighter planets is an ideal first target.

6.

Locate the object in the finder, center it, and then look through the telescope.

7.

Turn the focus knob on your G-8N until the image is sharp.

8.

Take your time and study your subject. If looking at the Moon, look for small detail in the craters.

That’s all there is to using your Celestron Newtonian telescope. However, don’t limit your view of an object to a single eyepiece. After observing an object for a few minutes, try using a different optional eyepiece, perhaps a more powerful one. This gives you an idea of how the field of view changes. Center your target and refocus.

Once again, if looking at the Moon you will be looking at a few craters at one time.

Use the slow motion knobs to scan the lunar surface.

Calculating

Magnification

As implied in the previous section, you can change the power of your

Celestron telescope just by changing the eyepiece (ocular). To determine the magnification for your telescope, simply divide the focal length of the telescope

(1000mm) by the focal length of the eyepiece you are using. In equation format, the formula looks like this:

Focal Length of Telescope (mm)

Magnification = —————————————————

Focal Length of Eyepiece (mm)

Let’s take an example to see how this formula works. If you were using the standard 20mm eyepiece supplied with your C150-HD or G-8N, you simply divide the focal length of the telescope (1000mm) by the focal length of the eyepiece

(20mm). 1000mm divided by 20mm yields a magnification of 50 power.

Although the power is variable, each instrument has a limit to the highest useful magnification. The general rule is that 60 power can be used for every inch of aperture. For example, the G-8N has a mirror diameter of 8". Multiplying 8 by 60 gives a maximum useful magnification of 480 power. Although this is the maximum useful magnification, most observing is done in the range of 20 to 35 power for every inch of aperture, which for the G-8N is between 160 and 280 power.

Determining Field of

V i e w

Determining the field of view is important if you want to get an idea of the angular size of the object you are observing. To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer) by the magnification. As you can see, before you determine the field of view, you must first calculate the magnification. In equation format, the formula looks like this:

Apparent Field of Eyepiece

True Field = ———————————————

Magnification

Using the example we started with above, we can determine the field of view using the same 20mm eyepiece. The 20mm eyepiece has an apparent field of view of approximately 52°. Divide the 52° by the magnification, which is 50 power. This yields an actual field of 1.04°, or a little more than a degree.

This formula gives you the true field of view in degrees. To convert degrees to feet at 1,000 yards, which is more commonly used for terrestrial viewing, simply multiply by 52.5. Continuing with our example, 1.04 times 52.5

produces a field size of 55 feet at 1,000 yards.

The apparent field of each eyepiece that Celestron manufactures is found in the Celestron accessory catalog (#93685).

Telescope Basics • 31

A S T R O N O M Y B A S I C S

This section deals with observational astronomy in general. It includes information on the night sky, polar alignment, and using your telescope for astronomical observations.

The Celestial Coordinate System

In order to help find objects in the sky, astronomers use a celestial coordinate system which is similar to our geographical coordinate system here on Earth.

The celestial coordinate system has poles, lines of longitude and latitude, and an equator. For the most part, these remain fixed against the background stars.

The celestial equator runs 360 degrees around the Earth and separates the northern celestial hemisphere from the southern. Like the Earth’s equator it bears a reading of zero degrees. On Earth this would be latitude. However, in the sky this is now referred to as declination, or DEC for short. Lines of declination above and below the celestial equator are labeled for their angular distance from the equator. The lines are broken down into degrees, minutes, and seconds of arc. Declination readings south of the equator carry a minus sign (-) in front of the number and those north are often preceded by a plus sign

(+).

The celestial equivalent of longitude is called Right Ascension, or R.A. for short. Like the Earth’s lines of longitude, they run from pole to pole and are evenly spaced 15 degrees apart. Although the longitude lines are separated by an angular distance, they are also a measure of time. Each line of longitude is one hour apart from the next. Since the Earth rotates once every 24 hours, there are 24 lines total. The R.A. coordinates are marked off in units of time.

It begins with an arbitrary point in the constellation of Pisces designated as 0 hours, 0 minutes, 0 seconds. All other points are designated by how far (i.e., how long) they lag behind this coordinate after it passes overhead moving toward the west.

Your Celestron telescope comes equipped with setting circles that translate the celestial coordinates into a precise location for the telescope to point. The setting circles will not work properly until you have polar aligned the telescope and set the R.A. setting circle. Note that the process of polar alignment sets the declination setting circle.

90

60

Declination

30

22

23

0

1 2 3

4

5

6

Right

Ascension

Figure 4-1

32 • Astronomy Basics

Motion of the Stars

Like the Sun, the stars also appear to move across the sky. This motion is caused by the Earth’s rotation. For observers in the northern hemisphere, all stars appear to move around the north celestial pole. For observers in the southern hemisphere, all stars appear to move around the south celestial pole. This means that over a 24hour period, any given star will scribe out a complete circle around its respective celestial pole. The farther you move away from the celestial pole, the larger this circle becomes and is largest at the celestial equator. Stars near the celestial equator rise in the east and set in the west. However, stars near the celestial poles are always above the horizon. They are said to be circumpolar because they don’t rise and set. You will never see the stars complete one circle because the sunlight during the day washes out the starlight. However, part of this circular motion of stars in this region of the sky can be seen by setting up a camera on a tripod and opening the shutter for a couple of hours. The processed film will reveal circular arcs that are centered on the pole. This information will be useful for certain methods of polar alignment.

Figure 4-2

All stars appear to rotate around the celestial poles. However, the appearance of this motion varies depending on where you are looking in the sky. Near the north celestial pole the stars scribe out recognizable circles centered on the pole (1). Stars near the celestial equator also follow circular paths around the pole. But, the complete path is interrupted by the horizon. These appear to rise in the east and set in the west (2).

Looking toward the opposite pole, stars curve or arc in the opposite direction scribing a circle around the opposite pole (3).

Astronomy Basics • 33

Polar Alignment

Definition:

In order for the telescope to track the stars it must meet two criteria. First, you need a drive motor that will move at the same rate as the stars. For the G-8N there are two optional motor drives (#93518 and #93523) that can be fitted to it. For the C150-HD there are also two optional motor drives (#93517 and #93522). The second thing you need is to set the telescope’s axis of rotation so that it tracks in the right direction. Since the motion of the stars across the sky is caused by the Earth’s rotation about its axis, the telescope’s axis must be made parallel to the Earth’s axis.

Polar alignment is the process by which the telescope’s axis of rotation is aligned (made parallel) with the Earth’s axis of rotation. Once aligned, a telescope with a clock drive will track the stars as they move across the sky.

The result is that objects observed through the telescope will appear stationary

(i.e., they will not drift out of the field of view). If your telescope does not use a motor drive, all objects in the sky (day or night) will drift out of the field. This apparent motion is caused by the Earth’s rotation. Even if you are not using a motor drive, polar alignment is still desirable since it will reduce the number of corrections needed to follow an object and will limit all corrections to one axis

(R.A.). There are several methods of polar alignment, all of which work on a similar principle, but are performed somewhat differently. Each method will be considered separately, beginning with the easier methods and working to the more difficult, but more precise.

Although there are several methods mentioned here, you will never use all of them during one particular observing session. Instead, you may use only one if it is a casual observing session. Or, if you plan on astrophotography, you may use two methods — one for rough alignment followed by a more accurate method.

The polar axis is the axis around which the telescope rotates when moving the telescope in right ascension. This axis remains stationary as the telescope moves in right ascension and declination.

34 • Astronomy Basics

Figure 4-3

When the telescope’s axis of rotation is parallel to the Earth’s axis, stars viewed through the telescope appear stationary when using a motor drive.

Finding the Pole

Figure 4-4

The position of the Big

Dipper changes throughout the year and throughout the night.

Definition:

For each hemisphere, there is a point in the sky around which all the other stars appear to rotate. These points are called the celestial poles and are named for the hemisphere in which they reside. For example, in the northern hemisphere all stars move around the north celestial pole. When the telescope’s polar axis is pointed at the celestial pole, it is parallel to the

Earth’s rotational axis.

Many of the methods of polar alignment require that you know how to find the celestial pole by identifying stars in the area. For those in the northern hemisphere, finding the celestial pole is relatively easy. Fortunately, we have a naked eye star less than a degree away. This star, Polaris, is the end star in the handle of the Little Dipper (see figure 4-5). Since the Little Dipper (technically called Ursa Minor) is not one of the brightest constellations in the sky, it may be difficult to locate, especially from urban areas. If this is the case, use the two end stars in the bowl of the Big Dipper. Draw an imaginary line through them (about five times the distance between these two stars) toward the Little Dipper. They will point to Polaris. The position of the Big Dipper will change during the year and throughout the course of the night (see figure 4-4). When the Big Dipper is difficult to locate, try using Cassiopia.

Observers in the southern hemisphere are not as fortunate as those in the northern hemisphere. The stars around the south celestial pole are not nearly as bright as those around the north. The closest star that is relatively bright is

Sigma Octantis. This star is just within naked eye limit (magnitude 5.5) and lies 59 arc minutes from the pole. For more information about stars around the south celestial pole, please consult a star atlas.

While it may seem that pointing at the pole star produces a parallax effect, especially for observers near the equator, this effect is negligible since Polaris is so far away.

The north celestial pole is the point in the northern sky around which all stars appear to rotate. The counterpart in the southern hemisphere is referred to as the south celestial pole.

Figure 4-5

The two stars in the front of the bowl of the Big Dipper point to Polaris which is less than one degree from the true (north) celestial pole. Cassiopia, the “W” shaped constellation is on the opposite side of the pole from the Big Dipper. The North

Celestial Pole (N.C.P.) is marked by the “+” sign.

Astronomy Basics • 35

36 • Astronomy Basics

Latitude Scales

The easiest way to polar align a telescope is with a latitude scale. Unlike other methods that require you to find the celestial pole by identifying certain stars near it, this method works off of a known constant to determine how high the polar axis should be pointed. The latitude range varies depending upon the telescope you own. The range for the CG-4 and CG-5 and is 40°.

The constant, mentioned above, is a relationship between your latitude and the angular distance the celestial pole is above the northern (or southern) horizon.

The angular distance from the northern horizon to the north celestial pole is always equal to your latitude. To illustrate this, imagine that you are standing on the north pole, latitude +90°. The north celestial pole, which has a declination of +90°, would be directly overhead (i.e., 90 above the horizon). Now let’s say that you move one degree south. Your latitude is now +89° and the celestial pole is no longer directly overhead. It has moved one degree closer toward the northern horizon. This means the pole is now 89° above the northern horizon. If you move one degree further south, the same thing happens again. As you can see from this example, the distance from the northern horizon to the celestial pole is always equal to your latitude.

If you are observing from Los Angeles, which has a latitude of 34°, then the celestial pole would be 34° above the northern horizon. All a latitude scale does then is to point the polar axis of the telescope at the right elevation above the northern (or southern) horizon. To align your telescope:

1.

Point your telescope due north. Use a landmark that you know faces north.

2.

Level the tripod by raising or lowering the legs as needed. There is a bubble level built into the CG-5 mount for this purpose.

3.

Adjust the telescope mount in altitude until the latitude indicator points to your latitude.

This method can be done in daylight, thus eliminating the need to fumble around in the dark. Although this method does NOT put you directly on the pole, it will limit the number of corrections needed when tracking an object. It will also be accurate enough for short exposure prime focus planetary photography (a couple of seconds) and short exposure piggyback astrophotography.

Pointing at Polaris

This method utilizes Polaris as a guidepost to the celestial pole. Since Polaris is less than a degree from the celestial pole, many amateurs simply point the polar axis of their telescope at Polaris. Although this is by no means a perfect alignment, it is close. To align using this method:

Align the finderscope with the main optical tube as described in the "Aligning the Finder" section earlier in the manual.

1 Set the telescope up so that the polar axis is pointing north and the counterweight shaft is rotated towards the ground.

2 Release the DEC clamp and move the telescope so that the optical tube is directly over the polar axis (see figure 4-6).

3 Move the mount in altitude and/or azimuth until Polaris is in the field of view of the finder. Rough azimuth adjustments can be made by moving the tripod .

4 Center Polaris using the fine altitude and azimuth controls (refer to figure 2-

5). Remember, do not move the telescope in R.A. or DEC. You want to adjust the direction the mount is pointing and you are using the telescope to see where the mount is pointing.

5 Once Polaris is in the finder it should also be centered in the telescope. If not, use the fine adjustment controls to center Polaris in the telescope field.

6 Rotate the Declination circle, just above the counterweight shaft, to read

90°. Do not move the Declination circle by hand after it is set.

Figure 4-6

Astronomy Basics • 37

NOTE:

Declination Drift

This method of polar alignment allows you to get the most accurate alignment on the celestial pole and is required if you want to do long exposure deep-sky astrophotography through the telescope. The declination drift method requires that you monitor the drift of selected guide stars. The drift of each guide star tells you how far away the polar axis is pointing from the true celestial pole and in what direction. Although declination drift is quite simple and straightforward, it requires a great deal of time and patience to complete when first attempted.

The declination drift method should be done after any one of the previously mentioned methods has been completed.

To perform the declination drift method you need to choose two bright stars.

One should be near the eastern horizon and one due south near the meridian.

Both stars should be near the celestial equator (i.e., 0° declination). You will monitor the drift of each star one at a time and in declination only. While monitoring a star on the meridian, any misalignment in the east-west direction will be revealed. While monitoring a star near the east/west horizon, any misalignment in the north-south direction will be revealed. As for hardware, you will need an illuminated reticle ocular to help you recognize any drift. For very close alignment, a Barlow lens is also recommended since it increases the magnification and reveals any drift faster.

When looking due south with the scope on the side of the mount, insert the diagonal so it points straight up. Insert a cross hair ocular and align the cross hairs to be parallel to declination and right ascension motion.

First choose your star near where the celestial equator and the meridian meet.

The star should be approximately ±1/2 hour of the meridian and ±5 degrees of the celestial equator. Center the star in the field of your telescope and monitor the drift in declination.

• If the star drifts south, the polar axis is too far east.

• If the star drifts north, the polar axis is too far west.

Make the appropriate adjustments to the polar axis to eliminate any drift.

Once you have managed to eliminate all drift, move to the star near the eastern horizon. The star should be 20 degrees above the horizon and ± 5 degrees off of the celestial equator.

• If the star drifts south, the polar axis is too low.

• If the star drifts north, the polar axis is too high.

Once again, make the appropriate adjustments to the polar axis to eliminate any drift. Unfortunately, the latter adjustments interact with the prior adjustments ever so slightly. So, repeat the process again to improve the accuracy checking both axes for minimal drift. Once the drift has been eliminated, the telescope is very accurately aligned. You will now be able to do prime focus deep-sky astrophotography for long periods.

If the eastern horizon is blocked, you may choose a star near the western horizon. However, you will have to reverse the polar high/low error directions. If using this method in the southern hemisphere, the procedure is the same as described above. However, the direction of drift is reversed.

38 • Astronomy Basics

Polar Alignment Finders

There are two finders specifically designed for polar alignment that can be used with the CG-4 and CG-5 mounts. These finders can be purchased as optional accessories for the C150-HD and G-8N. The first finder, known as the 7x50 Polaris finder (#51614), is used as a regular finder.

The second finder is the polar axis finderscope (#94221). Its sole purpose is polar alignment and can NOT be used to find objects in the telescope. Both these finders work on the same principle, but their methods of operation are slightly different.

These methods are generally easier than those already described and they are fairly accurate. For more information on both these finderscopes, refer to the Optional

Accessories section of this manual or ask for the Celestron accessory catalog

(#93685).

Aligning the R.A.

Setting Circle

Before you can use the setting circles to find objects in the sky you need to align the

R.A. setting circle. The declination setting circle is aligned during the polar alignment process. In order to align the R.A. setting circle you will need to know the names of a few of the brightest stars in the sky . If you don’t, they can be learned by using the Celestron Sky Maps (#93722) or consulting a current astronomy magazine. To align the R.A. setting circle:

1.

Locate a bright star near the celestial equator. The farther you are from the celestial pole the better your reading on the R.A. setting circle will be. The star you choose to align the setting circle with should be a bright one whose coordinates are known and easy to look up. (For a list of bright stars to align the R.A. setting circle, see the list at the back of this manual.)

2.

Center the star in the finder.

3.

Look through the main telescope and see if the star is in the field. If not, find it and center it.

4.

Start the optional motor drive so that it will track the star. If you are not using a motor drive the star will start to drift out of the field and you will need to center it again before setting the R.A. circle.

5.

Look up the coordinates of the star.

6.

Rotate the circle until the proper coordinates line up with the R.A. indicator

(the zero mark on the vernier scale). The R.A. setting circle should rotate freely.

As mentioned above, the declination setting circle is aligned during the process of polar alignment. There is no need to align it in the same manner as the R.A. setting circle.

Once you have finished this process you are ready to use the setting circles to locate objects in the night sky. See the section on “Using the Setting Circles” for specific information.

Astronomy Basics • 39

C E L E S T I A L O B S E R V I N G

Observing the Moon

Observing the

Planets

With your telescope set up, you are ready to use it for celestial observing.

This section covers visual observing of both solar system and deep-sky objects.

In the night sky, the Moon is a prime target for your first look because it is extremely bright and easy to find. Often, it is a temptation to look at the Moon when it is full. At this time, the face we see is fully illuminated and its light can be overpowering. In addition, little or no contrast can be seen during this phase.

One of the best times to observe the Moon is during its partial phases (around the time of first or third quarter). Long shadows reveal a great amount of detail on the lunar surface. At low power you will be able to see most of the lunar disk at one time. Change to higher power (magnification) to focus in on a smaller area. Keep in mind that if you are not using an optional motor drive, the rotation of the Earth will cause the Moon to drift out of your field of view.

You will have to manually adjust the telescope to keep the Moon centered.

This effect is more noticeable at higher power.

If you are using a motor drive and have polar aligned, the Moon will remain centered. Consult your local newspaper or a current astronomy magazine to find out when the Moon will be visible. Try using filters to increase contrast and bring out more detail on the lunar surface.

Other easy targets in the night sky include the five naked eye planets. You can see Venus go through its lunar-like phases. Mars can reveal a host of surface detail and one, if not both, of its polar caps. You will be able to see the cloud belts of Jupiter and the great Red Spot (if it is visible at the time you are observing). In addition, you will also be able to see the moons of Jupiter as they orbit this gas giant. Saturn with its beautiful ring system and Cassini's division are easily visible at moderate power. All you need to know is where to look. Most astronomy publications tell where the planets can be found in the sky each month.

40 • Celestial Observing

Figure 5-1

This scanned drawing of Jupiter provides a good representation of what you can expect to see with moderate magnification during good seeing conditions. The large, bright cloud belts should be immediately obvious. Smaller, faint belts become visible with practice and experience.

Observing the

S u n

WARNING:

Although overlooked by many amateur astronomers, solar observation is both rewarding and fun. However, because the Sun is so bright, special precautions must be taken (always use the proper solar filter) when observing our star so as not to damage your eyes or your telescope.

Never project an image of the Sun through the telescope. Because of the folded optical design, tremendous heat build-up will result inside the optical tube. This can damage the telescope and/or any accessories attached to the telescope.

SOLAR OBSERVING HINTS

• The best time to observe the Sun is in the early morning or late afternoon when the air is cooler.

• To locate the Sun without a finder, watch the shadow of the telescope tube until it forms a circular shadow.

Observing Deep-Sky

Objects

Deep-sky objects are simply those objects outside the boundaries of our solar system. They include star clusters, planetary nebulae, diffuse nebulae, double stars, and other galaxies outside our own Milky Way. The Celestron Sky

Maps (#93722) can help you locate the brightest deep-sky objects.

Most deep-sky objects have a large angular size. Therefore, low-to-moderate power is all you need to see them. Visually, they are too faint to reveal any color seen in long exposure photographs. Instead, they have a black and white appearance. And, because of their low surface brightness, they should be observed from a dark sky location. Light pollution around large urban areas washes out most nebulae making them difficult, if not impossible, to observe. Light Pollution

Reduction filters help reduce the background sky brightness, thus increasing contrast.

Celestial Observing • 41

42 • Celestial Observing

Using the Setting Circles

Once the setting circles are aligned you can use them to find any object with known coordinates.

1.

Select an object to observe. Use a seasonal star chart or planisphere to make sure the object you chose is above the horizon. As you become more familiar with the night sky, this will no longer be necessary.

2.

Look up the coordinates in an atlas or reference book.

3.

Move the telescope in declination until the indicator is pointing at the correct declination coordinate.

4.

Move the telescope in R.A. until the indicator points to the correct coordinate (do NOT move the R.A. circle). The telescope will track in R.A. as long as a motor drive is operating and the R.A. clamp is in the locked position.

5.

Look through the finder to see if you have located the object.

6.

Center the object in the finder.

7.

Look in the main optics using a low power eyepiece; the object should be there. The telescope will track in R.A. as long as the motor drive is operating.

8.

Repeat the process for each object observed throughout the observing session.

You may not be able to see fainter objects in the finder. When this happens, gradually sweep the telescope around until the object is visible.

The declination setting circle is scaled in degrees while the R.A. setting circle is incremented in minutes with a marker every fifth minute. As a result, the setting circles will get you close to your target, but not directly on it. Also, the accuracy of your polar alignment will also affect how accurately your setting circles read.

At the end of this manual there is a list of deep-sky objects well within reach of your Celestron telescope.

Star Hopping

You can use your setting circles to find these objects (as described earlier in this manual) or try star hopping. Star hopping is done by using bright stars to guide you to an object. Here are directions for two popular objects.

The Andromeda Galaxy, M31, is an easy first target. To find M31:

1.

Locate the constellation of Pegasus, a large square visible in the fall and winter months.

2.

Start at the star in the northeast corner. The star is Alpha (

α)

Andromedae.

3.

Move northeast approximately 7°. There you will find two stars of equal brightness — Delta (

δ) and Pi (π) Andromedae — about 3° apart.

4.

Continue in the same direction another 8°. There you will find two stars —

Beta (

β) and Mu (µ) Andromedae — about 3° apart.

5.

Move 3° northwest — the same distance between the two stars— to the

Andromeda galaxy. It is easily visible in the finder.

Figure 5-2

Star hopping to the Andromeda Galaxy is a snap to find since all the stars needed to do so are visible to the naked eye. Note that the scale for this star chart is different from the one on the following page which shows the constellation Lyra.

Celestial Observing • 43

Figure 5-3

Although the Ring Nebula lies between two naked eye stars, it may take a little time to locate since it is not visible in the finder. Note that the scale for this star chart is different from the one on the previous page which shows several constellations including Pegasus,

Triangulum, and Andromeda.

Star hopping may take some getting used to since you can see more stars through the finder than you can see with the naked eye. And, some objects are not visible in the finder. One such object is M57, the famed Ring Nebula. Here’s how to find it:

1.

Find the constellation of Lyra, a small parallelogram visible in the summer and fall months. Lyra is easy to pick out because it contains the bright star Vega.

2.

Start at the star Vega — Alpha ( α) Lyrae — and move a few degrees southeast to find the parallelogram. The four stars that make up this geometric shape are all similar in brightness, making them easy to see.

3.

Locate the two southern most stars that make up the parallelogram — Beta ( β) and Gamma ( γ) Lyrae (see figure 5-3).

4.

Point the finder half way between these two stars.

5.

Move about 1/2° toward Beta ( β) Lyrae, but remaining on a line that connects the two stars.

6.

Look through the telescope and the Ring Nebula should be in the telescope. Its angular size is quite small and, therefore, not visible in the finder.

These two examples should give you an idea of how to star hop to deep sky objects.

To use this method on other objects, consult any of the star atlases listed at the end of this book.

44 • Celestial Observing

Viewing Conditions

Viewing conditions affect what you can see through your telescope during an observing session. Conditions include transparency, sky illumination, and seeing.

Understanding viewing conditions and the affect they have on observing will help you get the most out of your telescope.

Transparency

Transparency is the clarity of the atmosphere and is affected by clouds, moisture, and other airborne particles. Thick cumulus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy skies absorb more light than clear skies making fainter objects harder to see and reducing contrast on brighter objects. Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when the night sky is inky black.

Sky Illumination

General sky brightening caused by the Moon, aurorae, natural airglow, and light pollution greatly affect transparency. While not a problem for the Moon, planets, and brighter stars, bright skies reduce the contrast of extended nebulae making them difficult, if not impossible, to see. To maximize your observing, limit deep-sky viewing to moonless nights far from the light polluted skies found around major urban areas. LPR filters enhance deep-sky viewing from light polluted areas by blocking unwanted light while transmitting light from certain deep-sky objects. You can, on the other hand, observe planets and stars from light polluted areas or when the Moon is out.

S e e i n g

Seeing conditions refer to the stability of the atmosphere and directly effects the clarity of star images and the amount of fine detail seen in extended objects like the planets. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bending depends on air density. Varying temperature layers have different densities and therefore bend light differently. Light rays from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric disturbances vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the “seeing” quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs. Seeing conditions are rated on a five-point scale where one is the worst and five is the best (see figure 5-4). Seeing conditions can be classified in one of three categories which are based on the cause.

Type 1 seeing conditions are characterized by rapid changes in the image seen through the telescope. Extended objects, like the Moon, appear to shimmer while point sources (i.e., stars) appear double. Type 1 seeing is caused by currents within or very close to the telescope tube. These currents could be caused by a telescope that has not reached thermal equilibrium with the outdoor surroundings, heat waves from people standing near the telescope, or heated dew caps. To avoid the problems associated with Type 1 seeing, allow your telescope approximately

20 to 30 minutes to reach thermal equilibrium. Once adjusted to the outdoor

Celestial Observing • 45

46 • Celestial Observing temperature, don’t touch the telescope tube with your hands. When pointing the telescope, hold the telescope by the star diagonal. If observing with others, make sure no one stands in front of or directly below the telescope tube.

The images produced by Type 2 seeing conditions don’t move as quickly as those produced by Type 1 conditions, but the images are quite blurry. Fine detail is lost and the contrast is low for extended objects. Stars are spread out and not sharp.

The source of Type 2 seeing is the lower atmosphere, most likely heat waves from the ground or buildings. To avoid the problems associated with Type 2 seeing, select a good observing site. Specifically, avoid sites that overlook asphalt parking lots or ploughed fields. Stay away from valleys and shorelines. Instead, look for broad hilltops or open grassy fields. Stable thermal conditions found near lakes and atmospheric inversions also tend to produce good seeing. If you can’t get a better location, wait until the early morning hours when the surroundings are uniformly cool and the seeing is generally better.

Type 3 seeing conditions are characterized by fast ripples, but sharp images.

In extended objects fine detail is visible, but the images shift around the field.

Stars are crisp points, but they shift small distances rapidly around the field.

The cause of Type 3 seeing is turbulence in the upper atmosphere which means the observer has less control over it. However, the effects of Type 3 seeing are generally less pronounced than the other two types. You can never really avoid Type 3 seeing. Your best bet is to wait until moments of steadiness. If the seeing is extremely bad, pack up and wait for a better night.

The conditions described here apply to both visual and photographic observations.

Figure 5-4

Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing conditions (left) to excellent conditions (right).

Most often, seeing conditions produce images that lie somewhere between these two extremes.

C E L E S T I A L P H O T O G R A P H Y

After looking at the night sky for awhile you may want to try photographing it.

Several forms of celestial photography are possible with your Celestron telescope.

The most common forms of celestial photography, in order of difficulty are: short exposure prime focus, piggyback, eyepiece projection, and long exposure deep sky.

Each of these is discussed in moderate detail with enough information to get you started. Topics include the accessories required and some simple techniques. More information is available in some of the publications listed at the end of this manual.

In addition to the specific accessories required for each type of celestial photography, there is the need for a camera — but not just any camera. The camera does not have to have many of the features offered on today’s state-ofthe-art equipment. For example, you don’t need auto focus capability or mirror lock up. Here are the mandatory features a camera needs for celestial photography. First, a ‘B’ setting which allows for time exposures. This excludes point and shoot cameras and limits the selection to 35mm SLR cameras.

Second, the ‘B’ or manual setting should not run off the battery. Many new electronic cameras use the battery to keep the shutter open during time exposures. Once the batteries are drained, usually after a few minutes, the shutter closes, whether you have finished with the exposure or not. Look for a camera that has a manual shutter when operating in the time exposure mode.

Olympus, Nikon, Minolta, Pentax, Canon and others have made such camera bodies.

The camera should have interchangeable lenses so you can attach it to the telescope and use a variety of lenses for piggyback photography. If you can’t find a new camera, you can purchase a used camera body that is not 100percent functional. The light meter does not have to be operational since you will be determining the exposure length manually.

Use a cable release with a locking function to hold the shutter open while you do other things. Mechanical and air releases are available at most camera stores.

Celestial Photography • 47

Short Exposure Prime

F o c u s

Short exposure prime focus photography is the best way to begin recording celestial objects. It is done with the camera attached to the telescope without an eyepiece or camera lens in place. To attach your camera, you need the T-adapter and a T-Ring for your specific camera (i.e., Minolta, Nikon, Pentax, etc.). The C150-HD and G-8N focuser have built-in T-adapter and are ready to accept a 35mm camera body. The T-

Ring replaces the 35mm SLR camera’s normal lens. Prime focus photography allows you to capture the entire solar disk (if using the proper filter) as well as the entire lunar disk. To attach your camera to your telescope:

1 Remove the eyepiece from the 1 1 /

4

" eyepiece holder.

2 Unthread the 1 1 /

4

" eyepiece holder from the focuser assembly. This will expose the male thread of the built-in T-adapter.

3 Thread the T-ring onto the exposed T-adapter threads.

4 Mount your camera body onto the T-Ring the same as you would any other lens.

With your camera attached to the telescope, you are ready for prime focus photography. Start with an easy object like the Moon. Here’s how to do it:

1.

Load your camera with film that has a moderate-to-fast speed (i.e., ISO rating). Faster films are more desirable when the Moon is a crescent.

When the Moon is near full, and at its brightest, slower films are more desirable. Here are some film recommendations:

• T-Max 100

• T-Max 400

• Any 100 to 400 ISO color slide film

• Fuji Super HG 400

2.

Center the Moon in the field of your telescope.

3.

Focus the telescope by turning the focus knob until the image is sharp.

4.

Set the shutter speed to the appropriate setting (see table 6-1).

5.

Trip the shutter using a cable release.

6.

Advance the film and repeat the process.

Lunar Phase ISO 50 ISO 100 ISO 200 ISO 400

Crescent 1 / 2 1 / 4 1 / 8 1 / 1 5

Quarter

F u l l

1 / 1 5

1 / 3 0

1 / 3 0

1 / 6 0

Table 6-1

1 / 6 0

1/125

1/125

1/250

Above is a listing of recommended exposure times when photographing the Moon at the prime focus of your Celestron Newtonian.

48 • Celestial Photography

Piggyback

The exposure times listed here should be used as a starting point. Always make exposures that are longer and shorter than the recommended time. Also, try bracketing your exposures, taking a few photos at each shutter speed. This will ensure that you will get a good photo. If using black and white film, try a yellow filter to reduce the light intensity and to increase contrast.

Keep accurate records of your exposures. This information is useful if you want to repeat your results or if you want to submit some of your photos to various astronomy magazines for possible publication!

The easiest way to enter the realm of deep-sky, long exposure astrophotography is via the piggyback method. Piggyback photography is done with a camera and its normal lens riding on top of the telescope. Through piggyback photography you can capture entire constellations and record large scale nebulae that are too big for prime focus photography. Because you are photographing with a low power lens and guiding with a high power telescope, the margin for error is very large. Small mistakes made while guiding the telescope will not show up on film. To attach the camera to the telescope, use the piggyback adapter screw located on the top of the tube mounting ring (see figure2-1). It will be neccessary to remove the finder scope bracket before attaching the camera. In order to guide the exposure, you will need an optional motor drive (#93518 or #93523).

As with any form of deep-sky photography, it should be done from a dark sky observing site. Light pollution around major urban areas washes out the faint light of deep-sky objects. You can still practice from less ideal skies.

1.

Polar align the telescope (using one of the methods described earlier) and start the motor drive.

2.

Load your camera with slide film, ISO 100 or faster, or print film, ISO 400 or faster!

3.

Set the f/ratio of your camera lens so that it is a half stop to one full stop down from completely open.

4.

Set the shutter speed to the “B” setting and focus the lens to the infinity setting.

5.

Locate the area of the sky that you want to photograph and move the telescope so that it points in that direction.

6.

Find a suitable guide star in the telescope eyepiece field of view. This is relatively easy since you can search a wide area without affecting the area covered by your camera lens. If you do not have an illuminated cross hair eyepiece for guiding, simply defocus your guide star until it fills most of the field of view. This makes it easy to detect any drift.

7.

Release the shutter using a cable release.

8.

Monitor your guide star for the duration of the exposure making the neccessary corrections needed to keep the star centered.

Celestial Photography • 49

50 • Celestial Photography

9.

Close the camera’s shutter.

As for lenses, use good ones that produce sharp images near the edge of the field. The lenses should have a resolving power of at least 40 lines per millimeter. A good focal length range is 50 to 500mm for lenses designed for 35mm cameras.

The exposure time depends on the film being used. However, five minutes is usually a good starting point. With slower films, like 100 ISO, you can expose as long as 45 minutes. With faster films, like 1600 ISO, you really shouldn’t expose more than 5 to 10 minutes. When getting started, use fast films to record as much detail in the shortest possible time. Here are proven recommendations:

• Ektar 1000 (color print)

• Konica 3200 (color print)

• Fujichrome 1600D (color slide)

• 3M 1000 (color slide)

• T-Max 3200 (black and white print)

• T-Max 400 (black and white print)

As you perfect your technique, try specialized films, that is films that are designed or specially treated for celestial photography. Here are some popular choices:

• Ektar 125 (color print)

• Fujichrome 100D (color slide)

• Tech Pan, gas hypered (black and white print)

As with all forms of photography, keep accurate records of your work. This information can be used later if you want to reproduce certain results or if you want to submit photos for possible publication.

Once you have mastered piggyback photography with wide angle and normal lenses, try longer focal length lenses. The longer the focal length, the more accurate your guiding must be. You can continue to increase the focal length of the lens until you are ready for prime focus photography with your Celestron telescope.

Collimation

T E L E S C O P E M A I N T E N A N C E

Care and Cleaning of the Optics

After you have set up your telescope and started using it, there are a few things to remember for future reference.

To minimize the need to clean your telescope, replace all lens covers once you have finished using it. Since the front of the telescope tube is open ALWAYS replace the front cover when the telescope is not in use. This will minimize the amount of contaminants from entering the optical tube and minimize the number of times your telescope needs to be cleaned.

The long tube of your Newtonian telescope acts as a dew shield to prevent moisture from building up on the primary mirror. However, on extremely damp nights, the tube may only slow the formation of dew on the primary mirror. If dew condenses on the primary mirror it can be removed with a hair dryer or by pointing the telescope at the ground.

Occasionally, dust and/or moisture may build up on the primary mirror of your telescope. Special care should be taken when cleaning any optical instrument so as not to damage the optics. Internal adjustments and cleaning should be done only by the Celestron repair department. If your telescope is in need of internal cleaning, please call the Celestron repair department for specific information on service.

Exact mirror alignment (i.e., collimation) of a fast f-number Newtonian reflector is necessary in order to obtain the best optical image quality possible. Although your telescope was fully collimated at the factory, you should check collimation to ensure that rough handling has not altered the alignment of the mirrors.

To determine whether or not recollimation is necessary, the telescope should be set up outside at night. It should be a still night and one in which you have let the telescope sit outside for 30 to 45 minutes before attempting collimation. You should also wait for a night with good seeing conditions and avoid looking over anything that produces heat waves (i.e., roof tops, car hoods, etc.).

Pick a bright star and center it in the field of the telescope. Study the image of the star while racking it in and out of focus using 30 to 60 power for every inch of aperture. For your G-8N this equates to about 240 to 480 power and for the C150-

HD is about 180 to 360 power.. If an unsymmetrical focus pattern is present, then it may be possible to correct this by recollimating only the primary mirror. Simply removing the ocular during the daytime and looking down the focus tube is NOT a satisfactory way of determining collimation. Read the procedural instructions through completely BEFORE attempting!

To star collimate, the telescope should be on either a motor driven (i.e., tracking) equatorial mount that is approximately polar aligned or pointed at a stationary star without the motor drive running. Polaris, the North Star, is the perfect collimation star for northern hemisphere observers since it appears motionless against the background sky long enough to perform the collimation procedure. Polaris is the last star in the handle of the Little Dipper (Ursa Minor) and its distance above the northern horizon is always equal to your latitude angle.

Maintenance • 51

IMPORTANT:

Prior to collimating the primary mirror holder, locate the three (3) screws on the end plate at the end of the tube. Unthread the three screws and remove the plate from the end of the tube. Under the end plate there are three (3) sets of two (2) screws. The shorter Allen screws push the mirror holder which is held by the longer outer screws.

In order to make an adjustment, the outer screw is loosened while the shorter screw is turned in or out. Then, the outer screw is tightened. Only one of the three (3) sets is adjusted at a time. Normally motions on the order of 1/8 turn will make a difference, with only about 1/2 to 3/4 turn being the maximum required.

Do NOT remove or back out the holder screws more than one (1) to two (2) turns!

With Polaris or a bright star centered in the field of view, focus with your highest power eyepiece (i.e., one with the shortest focal length). This includes eyepieces in the 4mm to 6mm range. The star should be well centered to avoid confusing collimation problems with coma, a problem common to all Newtonian telescopes especially near the edge of the field. If you notice a flare in the star at one side

(same side) just as you go inside and outside of exact focus, then collimation will help sharpen the image.

Take note of the direction of the flare. For example, if the flare is toward the 3 o’clock position in the field of view, then you must adjust the screw or combination of collimation screws necessary to move the star TOWARD the direction of the flaring. In this case you want to move the star with the adjusting screw to the right, toward the 3 o’clock position in the eyepiece field of view. It may only be necessary to adjust the screw to move the star from the center to about half way or less toward the field’s edge (for higher power oculars). Prior to making any adjustment, it is advisable to gently back off the pressure on the three (3) outer screws to where they are snug, yet easily loosened without moving the telescope unnecessarily.

Collimation adjustments are best made while viewing the star’s position in the field of view while turning the adjustment screws. This way you can see exactly which way the movement occurs. It may be helpful for two people working together, while one views and instructs the other which screws are correctly turned and by how much. Start by loosening the outer screws and advancing an inner screw to see if the motion is correct. If not, undo what you did and try another set of screws.

After making the first of each adjustment, it is necessary to reaim the telescope tube to center the star again in the field of view. It can then be judged for symmetry by going just inside and outside of exact focus and noting the star’s pattern. Improvement should be seen if the proper adjustments are made. Since three (3) sets of screws are present, it may be necessary to move at least two (2) sets of screws to achieve the necessary mirror movement. Do NOT over tighten the outer holding screws!

Once in collimation, your telescope should not need additional collimation unless the telescope has been bumped or jarred severely. In fact, most observers will find the telescope’s collimation right out of the box to be satisfactory. Exact collimation is only necessary for discriminating observers that require optimal imagery. Adjusting the secondary mirror is NOT needed unless the telescope has been dropped or damaged. If it requires an adjustment, contact your local astronomy club for more detailed instructions, consult a telescope users handbook, or call the Celestron technical support department.

52 • Maintenance

O P T I O N A L A C C E S S O R I E S

The following is a partial list of optional accessories available for your Celestron

C150-HD and G-8N.

Barlow Lens - A Barlow lens is a negative lens that increases the focal length of a telescope. Used with any eyepiece, it doubles the magnification of that eyepiece. Celestron offers two Barlow lens in the 1-1/4" size for the C150-HD and G-8N. The 2x Ultima Barlow (#93506) is a compact triplet design that is fully multicoated for maximum light transmission and parfocal when used with the Ultima eyepieces. Model #93507 is a compact achromatic Barlow lens that is under three inches long and weighs only 4 oz. It works very well with all

Celestron eyepieces.

CD-ROM (93700) - Celestron and Software Bisque have joined together to present this comprehensive CD-ROM called The Sky™ Level 1 - for Celestron.

It features a 10,000 object database, 75 color images, horizontal projection, custom sky chart printing, zoom capability, Comet Hale-Bopp coordinates and more! A fun, useful and educational product. PC format.

Dual Axis Drive System - #93523

This drive motor, with drive corrector capabilities, is designed for Celestron’s

CG-5 Equatorial telescope mount. It precisely controls the telescope’s tracking speed during long, timed exposures of celestial objects, producing the best possible image sharpness. Drive correctors are a must for those with serious interest in astrophotography or CCD imaging.This precision, state-ofthe-art DC motor drive operates on D-Cell batteries. The hand controller module is very compact and fits easily in the palm of your hand. Motors for both axes are included, along with brackets, clutches and hardware.

Eyepieces - Like telescopes, eyepieces come in a variety of designs. Each design has its own advantages and disadvantages. For the 1-1/4" barrel diameter there are four different eyepiece designs available.

• Super Modified Achromatic (SMA) Eyepieces:

The SMA design is an improved version of the Kellner eyepiece. SMAs

are very good, economical, general purpose eyepieces that deliver a

wide apparent field, good color correction and an excellent image at the

center of the field of view. Celestron offers SMA eyepieces in the following focal lengths: 6mm, 10mm, 12mm,17mm and 25mm.

• Plössl - Plössl eyepieces have a 4-element lens designed for low-to-high power observing. The Plössls offer razor sharp views across the entire field, even at the edges! In the 1-1/4" barrel diameter, they are available in the following focal lengths: 6.3mm, 7.5mm, 10mm, 12.5mm, 17mm,

20mm, 26mm, 32mm and 40mm.

• Ultima - Ultima is not really a design, but a trade name for our 5-element, wide field eyepieces. They are available in the following focal lengths:

5mm, 7.5mm, 12.5mm, 18mm, 24mm, 30mm, 35mm, and 42mm. These eyepieces are all parfocal.

Optional Accessories • 53

54 • Optional Accessories

• Lanthanum Eyepieces (LV Series) - Lanthanum is a unique rare earth glass used in one of the field lenses of this new eyepiece. The Lanthanum glass reduces aberrations to a minimum. All are fully multicoated and have an astounding 20mm of eye relief — perfect for eyeglass wearers! They are available in the following focal lengths: 2.5mm, 4mm,

5mm, 6mm, 9mm, 10mm, 12mm, 15mm, 20mm and 25mm. Celestron also offers the LV Zoom eyepiece (#3777) with a focal length of 8mm to

24mm. It offers an apparent field of 40 o at 24mm and 60 o at 8mm. Eye relief ranges from 15mm to 19mm.

Eyepiece Filters - To enhance your visual observations of solar system objects, Celestron offers a wide range of colored filters that thread into the 1-1/

4" oculars. Available individually are: #12 deep yellow, #21 orange, #25 red,

#58 green, #80A light blue, #96 neutral density - 25%T, #96 neutral density -

13%T, and polarizing. These and other filters are also sold in sets.

Finderscopes - Finderscopes are used to help you locate objects in the main telescope. The larger the finder, the more you will see, making it easier to locate objects. One option for finders is the Polaris 7x50 Finder (#93785-8P).

It comes with the finderscope, bracket and Polaris Setting Plate.

Another tool for finding objects in the sky is the Star Pointer (#51630). The

Star Pointer is different from a finderscope in that you can use both eyes when pointing the telescope at an object. A partially reflective surface projects the image of an LED illuminated pinpoint into the line of sight. Just align the illuminated pinpoint with the object you are interested in and the object will be in the main telescope.

Night Vision Flashlight - (#93588) - Celestron’s premium model for astronomy, using two red LEDs to preserve night vision better than red filters or other devices. Brightness is adjustable. Operates on a single 9 volt battery

(included).

Light Pollution Reduction (LPR) Filters (#94126A)- This 1 1 /

4

" filter is designed to enhance your views of deep sky astronomical objects when viewed from urban areas. LPR Filters selectively reduce the transmission of certain wavelengths of light, specifically those produced by artificial lights. This includes mercury and high and low pressure sodium vapor lights. In addition, they also block unwanted natural light (sky glow) caused by neutral oxygen emission in our atmosphere.

Micro Guide Eyepiece (#94171) - This multipurpose 12.5mm illuminated reticle can be used for guiding deep-sky astrophotos, measuring position angles, angular separations, and more. The laser etched reticle provides razor sharp lines and the variable brightness illuminator is completely cordless.

Moon Filter (94119-A) - Celestron’s Moon Filter is an economical eyepiece filter for reducing the brightness of the moon and improving contrast, so greater detail can be observed on the lunar surface. The clear aperture is

21mm and the transmission is about 18%.

Single Axis Motor Drive System - #93518

By adding the MDCG-5 Drive System to your mount, you add the capacity to automatically track objects in the sky, a convenience you’ll be sure to enjoy during long viewing or astrophotography sessions, when manual tracking can become tiring. Furthermore, the Drive System will enhance high-power visual observing. It attaches to the R.A. (east/west) drive axis of your CG-5 Mount and will drive the telescope at the normal sidereal rate as well as allowing you to guide at 2x and 4x sidereal. Power is supplied via a DC battery pack.

Planisphere (93720) - A simple and inexpensive tool for all levels of observers, from naked eye viewers to users of highly sophisticated telescopes. The

Celestron Planisphere makes it easy to locate stars for observing and is a great planet finder as well. A map of the night sky, oriented by month and day, rotates within a depiction of the 24 hours of the day, to display exactly which stars and planets will be visible at any given time. Ingeniously simple to use, yet quite effective. Made of durable materials and coated for added protection. Celestron Planispheres come in three different models, to match the latitude from which you’re observing:

For 20

For 30

For 40

° to 40 ° of latitude

° to 50 ° of latitude

° to 60 ° of latitude

#93720-30

#93720-40

#93720-50

Polarizing Filter Set (#93608) - The polarizing filter set limits the transmission of light to a specific plane, thus increasing contrast between various objects. This is used primarily for terrestrial, lunar and planetary observing.

Polar Axis Finderscope (#94221) - This useful accessory speeds accurate polar alignment by providing a means of visually aligning your German equatorial mount with Polaris and true north. The finderscope has an eyepiece with etched reticle for quick polar alignment.

Sky Maps (#93722) - Celestron Sky Maps are the ideal teaching guide for learning the night sky. You wouldn’t set off on a road trip without a road map, and you don’t need to try to navigate the night sky without a map either. Even if you already know your way around the major constellations, these maps can help you locate all kinds of fascinating objects.

T-Ring - The T-Ring couples your 35mm SLR camera body to the T-Adapter, radial guider, or tele-extender. This accessory is mandatory if you want to do photography through the telescope. Each camera make (i.e., Minolta, Nikon,

Pentax, etc.) has its own unique mount and therefore, its own T-Ring.

Celestron has 9 different models for 35mm cameras.

A full description of all Celestron accessories can be found in the

Celestron accessory catalog (#93685).

Optional Accessories • 55

M21

M22

M23

M24

M25

M26

M27

M28

M29

M30

M11

M12

M13

M14

M15

M16

M17

M18

M19

M20

M31

M32

M33

M34

M35

M1

M2

M3

M4

M5

M6

M7

M8

M9

M10

The Messier Catalog, compiled by Charles Messier, was the first extensive listing of star clusters and nebulae.

Messier’s primary observational purpose was to discover comets. He compiled this list so that others searching for comets would not be confused by these objects. His list still remains popular today because all of these objects are easily visible in amateur telescopes.

R.A.

H M S

Crab Nebula NGC 1952

NGC 7089

NGC 5272

NGC 6121

NGC 5904

NGC 6405

NGC 6475

NGC 6523

NGC 6333

NGC 6254

Tau

Aqr

CVn

Sco

Ser

Sco

Sco

Sgr

Oph

Oph

5 34.5

21 33.5

13 42.2

16 23.6

15 18.5

17 40.0

17 54.0

18 03.7

17 19.2

16 57.2

22 01

-00 49

28 23

-26 32

2 05

-32 13

-34 49

-24 23

-18 31

-4 06

4.2

3.3

5.8

7.9

6.6

8.4

6.5

6.4

5.9

5.8

P. Neb.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Op. Cl.

Op. Cl.

D. Neb.

Gl. Cl.

Gl. Cl.

Butterfly Cluster

Lagoon Nebula

Wild Duck Cluster

Hercules Cluster

NGC 6705

NGC 6218

NGC 6205

NGC 6402

NGC 7078

NGC 6611

NGC 6618

NGC 6613

NGC 6273

NGC 6514

NGC 6531

NGC 6656

NGC 6494

NGC 6603

IC 4725

NGC 6694

NGC 6853

NGC 6626

NGC 6913

NGC 7099

NGC 224

NGC 221

NGC 598

NGC 1039

NGC 2168

Sct

Vul

Sgr

Cyg

Cap

Sgr

Sgr

Sgr

Sgr

Sgr

Sct

Oph

Her

Oph

Peg

Ser

Sgr

Sgr

Oph

Sgr

And

And

Tri

Per

Gem

18 04.7

18 36.4

17 56.9

18 16.4

18 31.7

18 45.2

19 59.6

18 24.6

20 23.0

21 40.4

18 51.1

16 47.2

16 41.7

17 37.6

21 30.0

18 18.9

18 20.8

18 19.9

17 02.6

18 02.4

0 42.7

0 42.7

1 33.8

2 42.0

6 08.8

-22 30

-23 54

-19 01

-18 29

-19 15

-9 24

22 43

-24 52

38 32

-23 11

-6 16

-1 57

36 28

-3 15

12 10

-13 47

-16 11

-17 08

-26 16

-23 02

41 16

40 52

30 39

42 47

24 20

8.0

8.1

6.9

6.6

7.5

5.9

5.1

5.5

4.5

4.6

3.4

8.2

5.7

5.2

5.1

6.0

7.0

6.9

7.2

8.5

5.8

6.6

5.9

7.6

6.4

Op. Cl.

Gl. Cl.

Op. Cl.

Op. Cl.

Op. Cl.

Op. Cl.

P. Neb.

Gl. Cl.

Op. Cl.

Gl. Cl.

Op. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

D. Neb.

D. Neb.

Op. Cl.

Gl. Cl.

D. Neb.

Sp. Gx.

El. Gx.

Sp. Gx.

Op. Cl.

Op. Cl.

Eagle Nebula

Omega Nebula

Trifid Nebula

Dumbbell Nebula

Andromeda Galaxy

Pinwheel Galaxy

56 • The Messier Catalog

NGC 6779

NGC 6720

NGC 4579

NGC 4621

NGC 4649

NGC 4303

NGC 6266

NGC 5055

NGC 4826

NGC 3623

NGC 3627

NGC 2682

NGC 4590

NGC 6637

NGC 6681

NGC 6838

NGC 6981

NGC 6994

NGC 628

NGC 6864

NGC 650-1

NGC 1068

NGC 2068

NGC 1904

NGC 6093

NGC 1960

NGC 2099

NGC 1912

NGC 7092

NGC 2287

NGC 1976

NGC 1982

NGC 2632

NGC 2437

NGC 2422

NGC 2548

NGC 4472

NGC 2323

Pup

Pup

Hya

Vir

Mon

NGC 5194-5 CVn

NGC 7654 Cas

NGC 5024

NGC 6715

NGC 6809

Com

Sgr

Sgr

Aur

Aur

Aur

Cyg

UMa

CMa

Ori

Ori

Cnc

Tau

Sge

Aqr

Aqr

P s c

Sgr

Leo

Cnc

Hya

Sgr

Sgr

Per

Cet

Ori

Lep

Sco

Lyr

Lyr

Vir

Vir

Vir

Vir

Oph

CVn

Com

Leo

M66

M67

M68

M69

M70

M71

M72

M73

M74

M75

M56

M57

M58

M59

M60

M61

M62

M63

M64

M65

M76

M77

M78

M79

M80

M46

M47

M48

M49

M50

M51

M52

M53

M54

M55

M36

M37

M38

M39

M40

M41

M42

M43

M44

M45

11.5

8.8

8.0

8.0

7.2

8.3

9.4

9.2

8.6

9.0

6.9

8.2

7.7

8.1

9.7

6.6

8.6

8.5

9.3

8.2

9.0

9.8

9.8

8.8

8.1

6.9

7.7

7.7

7.0

6.1

4.4

5.8

8.4

5.9

4.5

4.0

9.0

3.1

1.2

6.0

5.6

6.4

4.6

8.0

12 59

11 49

-26 45

-32 21

-32 18

18 47

-12 32

-12 38

15 47

-21 55

30 11

33 02

11 49

11 39

11 33

4 28

-30 07

42 02

21 41

13 05

51 34

0 01

0 03

-24 33

-22 59

-14 49

-14 30

-5 48

8 00

-8 20

47 12

61 35

18 10

-30 29

-30 58

34 08

32 33

35 50

48 26

58 05

-20 44

-5 27

-5 16

19 59

24 07

11 20.3

8 50.3

12 39.5

18 31.4

18 43.2

19 53.7

20 53.5

20 58.0

1 36.7

20 06.1

19 16.6

18 53.6

12 37.7

12 42.0

12 43.7

12 21.9

17 01.2

13 15.8

12 56.7

11 18.9

1 42.2

2 42.7

5 46.7

5 24.2

16 17.0

7 41.8

7 36.6

8 13.8

12 29.8

7 03.0

13 29.9

23 24.2

13 12.9

18 55.1

19 40 .0

5 36.3

5 52.0

5 28.7

21 32.3

12 22.2

6 47.0

5 35.3

5 35.5

8 40.0

3 47.5

Sp. Gx.

Op. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Gl. Cl.

ast

S

Gl Cl.

Gl. Cl.

P. Neb.

Sp. Gx.

El. Gx.

El. Gx.

Sp. Gx.

Gl. Cl.

Sp. Gx.

Sp. Gx.

Sp. Gx.

P. Neb.

Sp. Gx.

D. Neb.

Gl. Cl.

Gl. Cl.

Op. Cl.

Op. Cl.

Op. Cl.

El. Gx.

Op. Cl.

Sp. Gx.

Op. Gx.

Gl. Cl.

Gl. Cl.

Gl. Cl.

Op. Cl.

Op. Cl.

Op. Cl.

Op. Cl.

dbl

Op. Cl.

D. Neb.

D. Neb.

Op. Cl.

Op. Cl.

Great Orion Nebula

Beehive Cluster

Pleiades

Whirlpool Galaxy

Ring Nebula

Sunflower Galaxy

Black Eye Galaxy

Leo’s Triplet

Leo’s Triplet

Cork Nebula

The Messier Catalog • 57

NGC 3031

NGC 3034

NGC 5236

NGC 4374

NGC 4382

NGC 4406

NGC 4486

NGC 4501

NGC 4552

NGC 4569

NGC 4548

NGC 6341

NGC 2447

NGC 4736

NGC 3351

NGC 3368

NGC 3587

NGC 4192

NGC 4254

NGC 4321

NGC 5457

NGC 5457

NGC 581

NGC 4594

NGC 3379

NGC 4258

NGC 6171

NGC 3556

NGC 3992

NGC 205

M91

M92

M93

M94

M95

M96

M97

M98

M99

M100

M81

M82

M83

M84

M85

M86

M87

M88

M89

M90

M101

M102

M103

M104

M105

M106

M107

M108

M109

M110

Com

Her

Pup

CVn

Leo

Leo

UMa

Com

Com

Com

UMa

UMa

Hya

Vir

Com

Vir

Vir

Com

Vir

Vir

UMa

UMa

Cas

Vir

Leo

CVn

Oph

UMa

UMa

And

9 55.8

9 56.2

13 37.7

12 25.1

12 25.4

12 26.2

12 30.8

12 32.0

12 35.7

12 36.8

12 35.4

17 17.1

7 44.6

12 50.9

10 44.0

10 46.8

11 14.9

12 13.8

12 18.8

12 22.9

14 03.2

14 03.2

1 33.1

12 40.0

10 47.9

12 19.0

16 32.5

11 11.6

11 57.7

0 40.3

69 04

69 41

-29 52

12 53

18 11

12 57

12 24

14 25

12 33

13 10

14 30

43 08

-23 52

41 07

11 42

11 49

55 01

14 54

14 25

15 49

54 21

54 21

60 42

-11 37

12 35

47 18

-13 03

55 40

53 23

41 41

Object Abbreviations:

• Sp. Gx. ................ Spiral Galaxy

• El. Gx. ................. Elliptical Galaxy

• Ir. Gx. ................... Irregular Galaxy

• Op. Cl. ................. Open Cluster

• Gl. Cl. .................. Globular Cluster

• D. Neb.................. Diffuse Nebula

• P. Neb.................. Planetary Nebula

NOTE: All coordinates for the objects in the Messier catalog are listed in epoch 2000.00.

10.2

6.5

6.2

8.1

9.7

9.2

11.2

10.1

9.8

9.4

9.2

8.6

9.5

9.8

9.5

6.8

8.4

7.6

9.3

9.2

8.3

8.1

10.0

9.8

8.0

7.7

7.7

7.4

8.3

9.3

Sp. Gx.

Gl. Cl.

Op. Cl.

Sp. Gx.

Sp. Gx.

Sp. Gx.

P. Neb.

Sp. Gx.

Sp. Gx.

Sp. Gx.

Sp. Gx.

Ir. Gx.

Sp. Gx.

El. Gx.

El. Gx.

El. Gx.

El. Gx.

Sp. Gx.

El. Gx.

Sp. Gx.

Bodes Nebula

Virgo A

Owl Nebula

Pin Wheel Nebula

Sp. Gx.

dup

Op. Cl.

Sp. Gx.

Sombrero Galaxy

El. Gx..

Sp. Gx.

Gl. Cl.

Sp. Gx.

Sp. Gx.

El. Gx.

58 • The Messier Catalog

The following is a list of bright stars that can be used to align the R.A. setting circle. All coordinates are in epoch 2000.0.

R.A.

Epoch 2000.0

R.A.

H M S

Sirius

Canopus

Arcturus

Rigel Kent.

Vega

CMa

Car

Boo

Cen

Lyr

06 45 09

06 23 57

14 15 40

14 39 37

18 36 56

-16 42 58

-52 41 44

+19 10 57

-60 50 02

+38 47 01

-1.47

-0.72

-0.72

+0.01

+0.04

Capella

Rigel

Procyon

Betelgeuse

Achernar

Hadar

Altair

Aldebaran

Spica

Antares

Fomalhaut

Pollux

Deneb

Beta Crucis

Regulus

Aur

Ori

CMi

Ori

Eri

Cen

Aqi

Tau

Vir

Sco

PsA

Gem

Cyg

Cru

Leo

05 16 41

05 14 32

07 38 18

05 55 10

01 37 43

14 03 49

19 50 47

04 35 55

13 25 12

16 29 24

22 57 39

07 45 19

20 41 26

12 47 43

10 08 22

+45 59 53

-08 12 06

+05 13 30

+07 24 26

-57 14 12

-60 22 22

+08 52 06

+16 30 33

-11 09 41

-26 25 55

-29 37 20

+28 01 34

+45 16 49

-59 41 19

+11 58 02

+0.05

+0.14

+0.37

+0.41

+0.60

+0.63

+0.77

+0.86

+0.91

+0.92

+1.15

+1.16

+1.28

+1.28

+1.36

List of Bright Stars • 59

FOR FURTHER READING

The following is a list of astronomy books that will further enhance your understanding of the night sky. The books are broken down by classification for easy reference.

Astronomy Texts

Astronomy Now .................................................................................................... Pasachoff & Kutner

Cambridge Atlas Of Astronomy .......................................................................... Audouze & Israel

McGraw-Hill Encyclopedia Of Astronomy ......................................................... Parker

Astronomy-The Evolving Universe ....................................................................... Zeilik

Atlases

Atlas Of Deep Sky Splendors ............................................................................. Vehrenberg

Sky Atlas 2000.0 .................................................................................................. Tirion

Sky Catalog 2000.0 Vol 1 & 2 ............................................................................ Hirshfeld & Sinnott

Uranometria Vol. 1 & 2 ........................................................................................ Tirion, Rappaport, Lovi

Magnitude 6 Star Atlas ........................................................................................ Dickinson, Costanzo, Chaple

NGC 2000.0 ........................................................................................................... Sinnott

General Observational Astronomy

The Cambridge Astronomy Guide ...................................................................... Liller & Mayer

A Complete Manual Of Amateur Astronomy ..................................................... Sherrod

The Guide To Amateur Astronomy ..................................................................... Newton & Teece

Visual Observation

Observational Astronomy For Amateurs ........................................................... Sidgwick

Astronomical Calendar ......................................................................................... Ottewell

Burnham’s Celestial Handbook Vols. 1, 2 & 3 ................................................. Burnham

The Planet Jupiter ................................................................................................. P e e k

Field Guide To The Stars & Planets .................................................................. Menzel & Pasachoff

Observe Comets ................................................................................................... Edberg & Levy

Astrophotography

Skyshooting .......................................................................................................... Mayall & Mayall

Astrophotography A Step-by-Step Approach .................................................... Little

Astrophotography For The Amateur ................................................................... Covington

Astrophotography ................................................................................................. Gordon

Astrophotography II .............................................................................................. Martinez

A Manual Of Celestial Photography ................................................................... King

Manual Of Advanced Celestial Photography ..................................................... Wallis & Provin

Colours Of The Stars ............................................................................................ Malin & Muirden

60 • Astronomy Books

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Tel. (310) 328-9560

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Item # 31058-INST

08-02

Price $10.00