Astronomy Insights
A Digital Supplement to
Astronomy Magazine
© 2017 Kalmbach Publishing Co.
Finding the
Right Telescope
November 2017 •
Telescopes 101
Buying your first telescope is a big step, especially if you’re not
sure what all those terms mean. So, to help you understand
what to look for in a quality telescope, the editors of Astronomy
magazine answer 11 of the most-asked questions.
know telescopes make
appear bigger, but
exactly do they do?
A telescope’s purpose is to collect light.
This property lets you observe objects
much fainter than you can see with your
eyes alone. Italian astronomer Galileo Galilei said it best when he declared that his
telescopes “revealed the invisible.”
Will my telescope be complete,
2to make
or will I need additional items
it work?
Most Celestron telescopes are complete
systems, ready for the sky as soon as you
unpack and assemble them. A few models
are “optical-tube assembly only.” This
means all you’re buying is the optics in the
tube with no tripod or accessories.
To see objects
through your scope in
their normal orientation,
you’ll need an accessory
called an image erector.
in observing.
3 I’mWhatinterested
should I do first?
Learn all you can about telescopes: what
types are available, the best accessories, and
what you’ll see through them. This publication is a good start because you’ll see a wide
range of options.
If a telescope interests you, visit www. to read more about it. You’ll
also find telescope reviews online at www. You’ll learn
what’s important to veteran observers when
they use a telescope. You’ll also get a feel for
mechanical quality, ease of use (including
portability), and extra features.
are objects through my
5 Why
telescope upside-down?
I buy binoculars
4 Should
before I buy a telescope?
I use my telescope for
6 Can
views of earthly objects?
No. The view through binoculars — especially near a city — won’t be what you
expect. They are, however, a valuable accessory at a dark site. Star clusters look great
through them, as do the Milky Way, meteor
trails, and the Moon. Learn more about
binoculars on page 11.
Because of the way a telescope focuses light,
the top of what you’re looking at is at the
bottom as it enters the eyepiece, and viceversa. You can re-flip the image with an
accessory called an “image erector,” but
you’ll lose a bit of the object’s light. And for
faint sky objects, you want the maximum
amount of light possible to reach your eye.
Besides, there’s no up or down in space, and
with most objects, you won’t even know
they’re upside-down.
Absolutely! Many nighttime observers
(usually those with smaller telescopes) also
use their telescopes for bird-watching or
other daytime nature-watching activities.
Here’s where the image erector (see #5)
comes in most handy.
Celestron’s Inspire 80AZ
is a complete package. It comes with the
telescope, tripod, eyepieces, and a lens cap
that doubles as a smartphone adapter for
capturing images. Celestron
Your telescope also can give you great nature
views, like the one of this painted bunting, in
the daytime. Howard B. Cheek
Light rays
Any mirror (or lens)
twice as large as
another captures four
times as much light.
So, a 6-inch mirror
collects four times
the light as one 3
inches across.
To eye
focal length
focal length
Astronomy: Roen Kelly
Telescopes flip the view of your target, which doesn’t matter at
all if you’re looking at an object in space. Astronomy: Roen Kelly
high winds, but a poor mount will transfer
vibrations even in a light breeze. So, be sure
your scope sits on a high-quality mount.
scope better
9 Isthana “go-to”
one without go-to?
A local astronomy club’s observing session, or
a star party like the one pictured here, is a great
place to “test-drive” a telescope. Celestron
Is there a way for me to
“test-drive” a telescope?
Yes. Look in your area for an astronomy
club and visit one of its meetings, which
usually occur monthly. There, you’ll find
others who enjoy the hobby and are willing
to share information and views through
their telescopes. At one of the club’s stargazing sessions, you’ll be able to look through
many different telescopes in a short period
and ask all the questions you like.
from quality optics,
what’s the most important
in a telescope system?
The mount, which is what the telescope’s
tube sits on. You can buy the finest optics
on the planet, but if you put them on a lowquality mount, you won’t be happy with
your system. No telescope can function in
Celestron’s FirstScope
is an ideal “grab and go”
telescope: It’s small, light,
and sets up on any level
surface. Celestron
Yes. A go-to telescope is one with a motor
or motors controlled by a built-in computer. Once set up for an evening’s observing, a go-to scope will save you lots of time
by moving to any sky object you select and
then tracking it. Even experienced observers prefer go-to scopes because they leave
more time to observe the sky.
NexStar SLT
offer go-to
technology at an
entry-level price.
10 IfdoesI useit myneedtelescope
Only if it has a motorized drive. In most
cases, telescope drives use direct current,
which means you can use batteries (including the one in your car). Adapters available
from the manufacturer will let
you plug your scope into an
electrical outlet.
the best
telescope for me?
It’s the one you’ll use the
most. If it takes an hour to
set up a scope, or if your
scope is large, heavy, and
difficult to move, you might
observe only a handful of times each
year. If, on the other hand, your scope is
quick to set up, you may use it several times
each week. A small telescope that’s used a
lot beats a big scope collecting dust in a
closet every time.
A go-to mount, like the one
included with Celestron’s
NexStar Evolution 8 telescope,
makes observing easy! A 10
hour internal battery plus
wireless telescope control via
WiFi makes the Evolution a
popular choice. Celestron
This adapter will let you
power your scope from a
car’s cigarette lighter. Celestron
Sponsored by Celestron
All about compound telescopes
• Compound telescopes employ a
ith regard to telescopes, “catadioptric” means “due to both the
reflection and refraction of light.”
These instruments also are known as “compound” telescopes and are hybrids that
have a mix of refractor and reflector elements in their design.
German astronomer Bernhard Schmidt
made the first compound telescope in 1930.
The Schmidt telescope had a spherical primary mirror at the back of the telescope
and a glass corrector plate in the front.
The Schmidt telescope was the precursor of today’s most popular design, the
Schmidt-Cassegrain telescope, or SCT. It
also incorporated elements by French professor Laurent Cassegrain. In the SCT, light
enters the tube through a corrector plate
and then hits the primary mirror at the
tube’s base, which reflects the light to a secondary mirror mounted on the corrector.
The secondary reflects light through a hole
in the primary mirror to the eyepiece,
which sits at the back of the scope.
combination of lenses and mirrors to
produce images.
• They have the most compact design.
• Manufacturers usually sell them as
complete systems.
Celestron’s NexStar
6SE utilizes a type of
compound telescope
called a SchmidtCassegrain. Celestron
The Advanced VX 8”
EdgeHD features
Celestron’s highest quality
optical technology on a
solid equatorial mount
that makes it the perfect
first choice for any aspiring
Primary mirror
Telescope tube
Secondary mirror
Focus knob
Corrector plate
A compound telescope combines a front lens with mirrors to focus light. This diagram shows a
Schmidt-Cassegrain telescope. Astronomy: Roen Kelly, after Celestron
• The number-one advantage of a compound telescope is its compact design. Such
instruments are often only one-quarter as long as comparably sized reflectors and
much shorter than refractors with half their aperture. This feature makes the compound telescope a great grab-and-go instrument.
• Like refractors, compound telescopes also have a closed tube. Adjusting to the outCelestron
In 1970, Celestron began making a
telescope that took amateur astronomers by storm: the Celestron 8, or the
C8 as observers soon called it. The
introduction of this scope started a
revolution. The orange-tubed
Celestron 8 SCT had many advantages — 8 inches of aperture, light
weight, better portability than any
8-inch reflector sold at the time, and
an f/10 optical system, which provided good magnification. A range of
ready-to-use accessories made celestial photography simple and popular.
The complete system included a
wedge users adjusted to their latitude
and a sturdy,
folding tripod.
Celestron based
several of its
current telescopes on this
proven design,
including the
CGEM, Edge HD,
CPC, NexStar SE,
and Advanced
Celestron’s original C8
Series lines.
side temperature, therefore, takes longer than with an open-tube reflector with the
same size mirror. To speed cooling, Celestron installs filtered cooling vents behind
the primary mirror of its top-end Schmidt-Cassegrain telescopes.
This field-tested workhorse offers crisp
views and superior tracking accuracy
you can trust for years
to come
Celestron’s razor-sharp EdgeHD
optical system and upgraded CPC
Deluxe mount combine to deliver the
ultimate observing experience
Our bestselling fully computerized 8”
SCT now just $999
B&H Photo – 800.947.9970 –
High Point Scientific – 800.266.9590 –
Optics Planet – 800.504.5897 –
Astronomics – 800.422.7876 –
OPT Telescopes – 800.483.6287 –
Woodland Hills – 888.427.8766 –
Adorama – 800.223.2500 –
Focus Camera – 800.221.0828 –
Start exploring the sky
Scan the Milky Way
One of the most pleasurable observing
experiences you can have under the summer or winter sky is simply scanning the
Milky Way through your telescope. It’s so
simple — just insert an eyepiece that gives a
wide field of view (one with a large number
on it), shut down your laptop, ignore your
observing guides, turn off your go-to drive,
and move your scope to and fro by hand.
Observe the Sun
You can double your
observing fun with
a safe solar filter.
A filter that fits
over the front of
your telescope is
the only kind to use.
Never look directly at
the Sun with your eye Observing the Sun
will allow you to use
or through any unfilyour scope during
tered telescope.
the daytime. Be sure
You can start your
to use a safe solar
solar observing by
filter. Alan Friedman
counting or sketching
sunspots. It’s fun, its’ easy, and sunspot
counts let you know just how active the Sun
is. People have been recording sunspot
numbers daily since 1749.
Jamie Cooper
Observe the Moon
The Moon has a face that’s always changing. But Full Moon is not the best time to
view it. That’s when there are few shadows,
so you’ll see little detail.
The best evening
views are between
New Moon and 2
days after First
Quarter. In the
morning before sunrise, view from
about 2 days before
Last Quarter to just
before New Moon.
The Moon offers a
Shadows are longer
changing face, superb
at these times, and
shadow details, and
lunar features really
thousands of
fascinating features.
stand out.
Mainly look along
the line dividing the
light and dark portions, called the terminator. There,
you’ll see mountaintops high enough to
catch sunlight while
Enjoy the Milky Way in the summer or winter, when it’s highest in the sky.
dark lower terrain
surrounds them. On
large crater floors, you can follow “wall
arcseconds, noted by the symbol ". One
shadows” cast by the sides of craters hunarcsecond (1") equals 1/3,600 of 1°. See the
dreds of feet high. All these features change table below for the double star separation
in real time, and the differences you can
your telescope can split.
see in just one night are striking.
Observe Jupiter
Next to the Sun and Moon, Jupiter has the
most detail. The planet’s four largest moons
look like bright stars generally in a line on
either side of Jupiter.
Along with the moons, two dark stripes
— the North and South Equatorial Belts
— are easy to see. If the atmosphere above
your site is steady, use higher magnifications (eyepieces with lower numbers
printed on them). You’ll see that Jupiter
looks a bit oblong because it spins fast and
is not a solid planet.
double stars
Although stars look
like a single point of
light to the naked
eye, your telescope
will split many of
Albireo, a star in the
constellation Cygnus
them into pairs.
the Swan, is just one
Observing double
of hundreds of
stars is easy, it
colorful double stars
doesn’t take a comyou can see through
plicated setup, you
your scope. Dietmar Hager
can observe from a
city, and targets exist for every size telescope. Plus, you’ll see lots of colors.
In addition to how bright each component of the double star is, one number will
let you know if your telescope can split it.
It’s the pair’s “separation” — the visual distance between the two stars. It’s given in
Tunç Tezel
Congratulations on your telescope purchase.
Here are some suggested objects to observe.
Observe Messier’s list
Charles Messier (1730–1817) was a French
comet-hunter. During his searches, he
encountered dozens of objects that looked
like comets but didn’t move against the
starry background.
In 1758, he discovered what he thought
was a comet. This object became the first
entry — M1 — in his famous catalog of
comet “imposters.” Working your way
through Messier’s list will introduce you to
some of the best and brightest star clusters,
nebulae, and galaxies.
The size of your telescope will influence which double stars you observe.
Bigger scopes can resolve smaller
separations. Use this table as a general rule to determine the minimum
double star separation your telescope
will split. Weather conditions may
affect your success.
you’ll split
Sponsored by Celestron
Astronomy tests
This setup is as close to “grab-and-go” astronomy as an 8-inch
Schmidt-Cassegrain telescope can be. by Craig and Tammy Temple
hen we saw the first mention of Celestron’s NexStar
Evolution 8 telescope, we
knew it would be a great
product. This review gave us
the opportunity for a “first look,” and,
wow, are we happy! While we have
been into astroimaging for some
time, we also have logged many
hours visual observing, and even
more recently.
As of late, we have begun joining a local group in doing some
outreach. Sharing nighttime views
with the public affords us more
opportunities to do visual astronomy
— and to show off this telescope.
Celestron’s NexStar Evolution telescopes come in
6-inch, 8-inch, and 9.25-inch versions. Astronomy
tested the 8-inch model for this review. ALL IMAGES
The package that arrived on our
doorstep included an 8-inch
Schmidt-Cassegrain telescope
optical tube assembly (OTA),
an alt-azimuth mount, a
height-adjustable tripod
with accessory tray,
Celestron’s NexStar+ hand
controller, a 1¼" star
diagonal, a red-dot
finder, an AC adapter
with U.S., European
Union, British, and
Australian plugs,
and two Plössl
eyepieces (40mm and 13mm), all standard.
The box additionally included a USB cable
and a serial cable, which are not standard.
Assembly of the system was straightforward and simple. As we followed the
instructions in the included manual, we
learned that a smart device (Apple iOS
devices with iOS 7.0 and later or an
Android device with Android 4.0) can control the mount. That intrigued us even
more. With the battery fully charged and
the free Celestron SkyPortal app downloaded and installed on our iPad, the only
thing we had to wait for was clear skies.
As far as setup goes, simply unplug the
mount from the A/C adapter, pick a spot
suitable for viewing, and set it down — no
need to worry about mount/tripod orientation. Level the mount using the built-in
bubble level on the tripod, orient the OTA
parallel to the ground and pointing to an
unobstructed view of the horizon, switch
on the power, connect to your smart device
(or use the hand controller), do a two- or
three-star alignment (if few bright stars are
available, you can use the Moon and/or a
planet), and you’re ready to go. Easy-breezy,
nice and easy!
Craig and Tammy Temple are a husband-wife
team who have enjoyed the great hobby of
astrophotography since 2007.
For our setup, we used two bright stars
and Saturn. As for telescope control, using
the iPad was not only simple but also really
fun. Celestron’s SkyPortal is a nice planetarium app that lets you simply touch a
target on the screen and command the
NexStar Evolution to “go to” that object. It
also has arrows for slewing the telescope.
The app lets you refine its accuracy by
adding up to 10 additional alignment
points. Simply tap a star on your screen, tap
“GoTo,” center the object in the eyepiece,
and then tap “Align.” With these features,
we found locating and tracking objects to
be so accurate that we used the manual
slewing — after the initial setup — only
when we viewed the Moon’s many features.
First light was a real treat because of the
simple setup and pleasing views of Saturn
and the Moon, which confirmed the quality
of the optics. And controlling the telescope
was a snap with the iPad.
Being avid astrophotographers, we had
to image something. We opted to start with
Saturn and the Moon. Short of an issue
with the Wi-Fi connection (for the iPad)
dropping a couple times, first light was a
success with both viewing and imaging.
Feeling satisfied, we called it a night and
found that breaking down the system was
even easier than setting it up.
More great features
As we continued to observe with this wonderful telescope, we found numerous features that helped us understand why
Celestron called it the “Evolution.” It really
is a next step for amateur astronomy.
One feature allows for setting the tracking rate to either “Sidereal,” “Lunar,”
“Solar,” or “Off.” You also can set the AntiBacklash in both altitude and azimuth to
eliminate any play between gears.
When you purchase one of Celestron’s NexStar
Evolution telescopes, you get a complete system, including the optical tube, computerized
go-to drive, and stainless-steel tripod.
Celestron NexStar Evolution 8
The NexStar
Evolution uses
famous SchmidtCassegrain
Another nice feature is the “Altitude
Slew Limits.” This prevents the telescope
from striking the mount when you attach
oversized accessories or when the optical
train is long. It also prevents the telescope
from slewing below obstructed horizons.
Also helpful is “Slew Buttons at Slow
Speeds.” This allows you to change the
direction of the slew buttons when you use
them at the three lowest slewing speeds.
Here’s a feature that tells us that the folks at
Celestron really do use their equipment.
How many times have observers wished
that a control button’s position corresponded to the direction the object would
move in the field of view? This setting can
change it to match.
If your mount is permanent or semipermanent, you’ll like “Hibernate Enabled.”
This convenient feature lets you save the
telescope alignment when powering off or
disconnecting the OTA from the mount.
Optical design: Schmidt-Cassegrain
Focal length: 2,032 millimeters
Focal ratio: f/10
Secondary mirror obstruction: 9.77%
Database: More than 120,000 objects
Optical tube length: 17 inches
(43 centimeters)
Total weight: 40.6 pounds
(18.4 kilograms)
Price: $1,599.95
Contact: Celestron
2835 Columbia Street
Torrance, CA 90503
[t] 310.328.9560
Three more minor but useful features
are “Battery Status” (displays voltage,
charging/discharging, and High, Medium,
or Low status), “Tray Lighting” (adjusts the
LED brightness of the accessory tray light),
and the USB charger (allows for charging a
smart device).
While the Evolution has even more features, they are not too different from those
on most “go-to” telescopes, so we will move
along. One thing worth mentioning is that
using the hand controller and a smart
device interchangeably during a session
does not work without realigning. What
this means is if you set up and align using a
smart device, then decide you would like to
use the hand controller, you will have to
repeat the setup and alignment with the
hand controller or vice-versa.
Because we are accustomed to a much
more involved setup with our normal rig
(i.e., lugging a heavy marine battery to
power the mount; spending time performing polar alignment; having to connect to a
laptop or PC for go-to capability; and being
limited to rather slow slew speeds), saying
that getting to use the NexStar Evolution 8
telescope package was a real treat is an
understatement. It was fantastic!
This package is definitely a winner for
the observer, and it even does a great job
imaging. You don’t often hear of an 8-inch
SCT package being called a “grab-and-go”
setup, but we wouldn’t hesitate to put it in
that category. With its portability, simple
setup, and ease of use, we would highly recommend it to any visual astronomer, especially those doing outreach, and also would
suggest it to someone interested in lunar
and planetary imaging.
For a limited time this holiday season, we’re offering huge
instant savings on Celestron’s breakthrough NexStar Evolution
HD telescope. Enjoy the night sky with fantastic views and
integrated WiFi at an unbeatable price.
StarSense technology aligns your telescope
in minutes with no user input
8” EdgeHD optics for razor sharp views
Integrated WiFi for wireless control with
your mobile device
LiFePO4 internal battery with 10-hour capacity
*Sale Valid 11/1/17-12/31/17
B&H Photo – 800.947.9970 –
High Point Scientific – 800.266.9590 –
Optics Planet – 800.504.5897 –
Astronomics – 800.422.7876 –
OPT Telescopes – 800.483.6287 –
Woodland Hills – 888.427.8766 –
Adorama – 800.223.2500 –
Focus Camera – 800.221.0828 –