Borg SWII Fork Mount User Instructions

Borg SWII Fork Mount User Instructions
SWII Fork Mount User Instructions
8/13/2003
SWII Fork Mount User Instructions
Introduction
This document describes the use of the versatile and lightweight Borg SWII
single-arm fork mount. The SWII fork is available alone (part #3101) for
mounting on a standard photo tripod, for use with a custom Borg Slik tripod
(part #3305), or included in a complete observing set with a Series 80 Borg
refractor.
The fork mount includes a quick-release for the optical tube assembly (OTA),
slow motion knobs in both axes, and graduated scales for use in equatorial
operation. It is intended for visual use only with lightweight scopes such as
the Borg Series 80 and mini Borg units.
Mounting Options
For mounting on a standard photo tripod, the SWII fork
includes a photo standard 3/8”-16 hole in its base.
This allows for mounting directly to common
photographic tripods such as Bogen tripods. With the
use of a threaded insert (not supplied but commonly
available at photographic equipment stores) the fork
may be mounted on tripods with the standard ¼”-20
screw or doubled-up on a tripod with an adjustable
photographic head already mounted.
For use with the ultra-compact Borg/Slik tripod, the
fork attaches with a special base that allows for easy
adjustment of tilt for alt-azimuth or equatorial
operation.
Attaching the Optical Tube Assembly
Attachment of the OTA to the fork head requires the use of the Series
80 tube holder (part #5503 shown at left), or the Universal Attachment
Block (part #3102 shown at right), which have the proper mating
quick-release dovetail interface. The Universal Attachment Block has
a ¼”-20 threaded hole which can accommodate a Mini Borg OTA,
camera, or any lightweight telescope with a standard photo tripod interface. When
using rings to hold the OTA, loosen the mount clutches and slide the OTA within
the rings to get to the best possible balance position to insure that the mount’s movements are smooth.
Hutech Corporation & ScienceCenter.Net © 2003
1
SWII Fork Mount User Instructions
8/13/2003
Alt-azimuth Operation
The Borg single-arm fork mount may be used directly in alt-az
mode as shown at left. Simply mount the fork on the tripod with its
base level and ignore the equatorial dial markings on each axis.
The slow motion knobs (dark gray) can be used for fine adjustment
of pointing. To rapidly position the scope, turn the clutch knobs
(light gray) counterclockwise to loosen them slightly and push the
scope to the desired position. Note that you should hold the OTA
firmly in one hand while releasing or tightening the clutches as an
unbalanced scope may suddenly swing free and hit the tripod.
In alt-az operation, one common problem with telescope mountings
is that viewing of zenith is restricted because the mount interferes
with the OTA when pointed vertically. When using the Borg/Slik
tripod, you can get around this by simply tilting the head back just
far enough for the OTA to clear the head and tripod.
If the fork head is attached to a
photo tripod, you can either use a
doubled-up mounting configuration (fork mount attached to the mount’s
photo head), or simply shorten a leg of the tripod. Note that shortening
a leg can cause the tripod arrangement to be unstable, so counterweighting the tripod may be necessary. Alternatively, for Borg Series
80 scopes, a Takahashi tube holder may be used in conjunction with
the Borg Universal Attachment Block as shown. The combination
allows the OTA to clear the head/tripod for viewing the zenith.
Hutech Corporation & ScienceCenter.Net © 2003
2
SWII Fork Mount User Instructions
8/13/2003
Equatorial Operation for Convenient Tracking
The Borg single-arm fork head also allows for equatorial operation in either the Northern or Southern
hemispheres, simplifying tracking of astronomical objects as the Earth rotates. This is especially handy in
conjunction with the slow motion controls when using high power for planetary viewing.
To use the fork in equatorial mode, alignment with the Earth’s axis of
rotation is required. Begin by rotating the entire tripod assembly so that
the RA axis of the fork mount is pointing north if you are in the northern
hemisphere or south if you are in the southern hemisphere. If you are
using a compass to determine the direction of the pole, be sure to
compensate for magnetic deviation for maximum accuracy.
Next, tilt the head back to align with
the pole. In the northern hemisphere
this can be accomplished at night
conveniently by sighting on Polaris,
which is less than 1 degree from the
Earth’s North Pole. Otherwise, set
the tilt to match the latitude of your
observing position. If the tripod itself
is level, you can use the fork’s built-in
latitude angle scale as shown at right.
Loosen the scale’s pivot screw slightly until the triangular scale can
swing freely. Then tilt the head back until the index mark is lined up
with your latitude.
Once you have aligned the mount with the Earth’s pole, you can then
maintain astronomical objects in view by simply turning the RA slow
motion control to compensate for the Earth’s rotation. Note that for
most applications, exact alignment with the pole is not necessary. If you are viewing at low powers
and/or not tracking an object for a long interval, rough alignment may be all that is necessary.
Misalignment of the polar axis will simply cause some drift in the Dec axis, necessitating occasional
corrections using the Dec slow motion control in addition to the RA tracking adjustments.
Using the Setting Circles
Setting circles are also provided on the Borg single-arm fork mount for convenience in locating objects for
which coordinates are given (e.g. comets or deep sky objects). To use the setting circles, the mount must
be polar aligned with as much accuracy1 as possible as described above.
The Declination (Dec) axis has a fixed scale under the dec clutch knob. When properly adjusted, pointing
the OTA perpendicular to the Right Ascension (RA) axis should result in a reading of zero degrees.
When pointing at the pole, the dial should read 90 degrees. If you are utilizing the universal attachment
block, insure that the OTA is mounted on the block parallel to the long axis of the attachment block.
When aligned, the reading of the Dec dial corresponds directly to the Dec coordinate in the sky where the
telescope is pointing.
The right ascension (RA) axis dial is designed for use in the Northern Hemisphere2. It is free to rotate
independent of the RA axis since as the Earth rotates, the dial must be adjusted accordingly. This also
1
Setting circle accuracy is, in practice, limited by the resolution of the setting circle scales as well as the accuracy with which the mount
is polar aligned. These are intended strictly for casual visual use and not for applications requiring high precision.
2
The RA marks must be corrected for Southern Hemisphere use with the equation RA(south)= 24-Reading (modulo 24).
Hutech Corporation & ScienceCenter.Net © 2003
3
SWII Fork Mount User Instructions
8/13/2003
means that when the RA setting circle is to be used to locate an object, it must first be rotated to match
the sky coordinates. This is done by pointing at a bright star with known coordinates, setting the RA circle
to match, and then moving the scope at the desired target’s coordinates using the setting circle readings.
For convenience, the RA dial is marked with the positions of six bright stars3 in red lettering. These have
been chosen so that at least one of these bright stars is above the horizon no matter what time of the
night or time of the year you happen to be observing:
Label
R
S
Al
An
Ad
B
Season
Spring
Spring
Summer
Summer
Fall
Winter
Star / Constellation
Regulus / Leo
Spica / Virgo
Altair / Aquila
Antares / Scorpius
Alpha Andromeda
Betelgeuse / Orion
RA
h
10
13h
19h
16h
00h
05h
m
08
25m
50m
29m
08m
55m
Dec
Magnitude
+12°
-11°
+09°
-26°
+29°
+07°
1.3
0.9
0.8
1.0
2.1
2.1
As an example, here are the steps for locating the winter object M42, the Orion Nebula:
1. Align the mount to Polaris (the north pole) as described in the previous section.
2. Using the lowest power eyepiece (H-50 in the Borg SWII set), center Betelgeuse, then rotate the
RA setting circle dial until ‘B’ is at the RA index mark.
3. Verify that the Dec reading is at the 7 degree mark. If it is within about 2 degrees, proceed to the
next step. Otherwise, readjust your polar alignment and try again (i.e. go back to step 1).
4. Now move the telescope to the coordinates of M42 (RA=05h35m, Dec=-5°) while watching the
setting circle scale readings. Move the telescope by releasing the clutches, push the scope close
to the target coordinates, tighten the clutches again, and then use the slow motion controls for
fine adjustment.
5. M42 should now be within the field of view of your eyepiece.
If you are having trouble locating objects, here are some suggestions:
•
•
•
•
•
•
3
Practice centering bright objects first.
Use an alignment star that is close to the target object.
Use the lowest possible power eyepiece when attempting to locate objects. If the object is not
within view after moving to the target coordinates, it could indicate that the polar alignment has
not been accurately set. If this is the case, carefully search around the coordinate point using the
slow motion controls of the mount.
Take care not to bump the tripod when moving between the alignment star and the target.
Center the alignment star carefully. This will insure the best possible accuracy when moving to
the target.
Do not delay going from the alignment star to the target. If you wait too long, rotation of the earth
will cause your pointing in RA to be off when you attempt to move to the target.
Alignment star markings are not intended for Southern Hemisphere use and should be disregarded.
Hutech Corporation & ScienceCenter.Net © 2003
4
SWII Fork Mount User Instructions
8/13/2003
Mount Adjustments
Occasionally, your mount may require some adjustments as described below. In all cases, be sure to use
the proper sized tool to avoid damaging screws or the mount.
•
Adjustment of the RA Axis Free Movement and Clutch Tension
1. Unscrew the RA clutch knob completely by turning it counter-clockwise until it comes off.
Take care to not lose the washer found on the shaft under the knob.
2. Remove the setting circle plastic dial.
3. Adjust the RA axis tension using the 3 Phillips screws found under the RA dial. Tighten the
screws to stiffen the resistance of the axis to turning or loosen them to reduce friction.
4. If necessary, adjust the 4 screws found on the opposite side of the axis from the clutch knob.
Rotate the base of the head until the screws are aligned with the 4 holes in the base so that a
screwdriver may be inserted for the adjustment.
5. Replace the RA dial and clutch knob. The RA dial should remain free to rotate.
•
Adjustment of the Dec Axis Free Movement and Clutch Tension
1. Unscrew the Dec clutch knob completely by turning it counter-clockwise until it comes off.
Take care to not lose the washer found on the shaft under the knob.
2. Remove the setting circle plastic dial. This is set in a fixed position with double-sided tape,
so it will have to be carefully pried off using a sharp edged tool. Note its position so that it
can be put back in the proper orientation when reassembling the Dec assembly.
3. Adjust the Dec axis tension using the 3 Phillips screws found under the dial. Tighten the
screws to stiffen the resistance of the axis to turning or loosen them to reduce friction.
4. If necessary, adjust the 4 screws found on the opposite side of the axis from the clutch knob.
Rotate the OTA interface side of the Dec axis until the screws are aligned with the 4 holes in
the OTA interface so that a screwdriver may be inserted for the adjustment.
5. Replace the Dec dial (taking care to restore the original alignment) and the Dec clutch knob.
If you’ve forgotten to mark the original alignment of the dial, remember that the dial should
read 90 degrees when the OTA is pointing perpendicular to the RA axis.
•
Adjustment of the RA or Dec Knob Play
1. Grip the knob firmly and use a screw driver to loosen the Philips screw located in the center
of the knob.
2. Grip the opposite end of the slow motion shaft tightly with pliers and turn the knob 30-45
degrees clockwise.
3. Tighten the Philips screw in the center of the knob to finish.
Note that this procedure corrects knob slippage on the slow motion shaft and not the backlash of
the control
•
Tightening the Borg/Slik Tripod Attachment
Over time, the attachment point of the fork head to the Borg/Slik tripod may become worn enough
to prevent the head from being tightly coupled, especially when tilted for equatorial mode
operation. In this case, place a washer between the attachment screw and the tripod holes as
shown.
Hutech Corporation & ScienceCenter.Net © 2003
5
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising