CLUTCH KNOBS AND BALANCING
R.A. and Dec. Clutch Knobs
1. What do they do?
The three R.A. and three Dec. C
LUTCH
K
NOBS
have the function of connecting the R.A. and Dec. axes to their
respective drive worm wheel gears. Their function is progressive, from no tension (axes free to move - as required
during correct balancing of the telescope) to a completely "locked up" state.
2. How can you find out what they really do?
As shipped, all
Mach1GTO
mounts have all three R.A. and Dec. C
LUTCH
K
NOBS
firmly hand tightened. This will give
you a good idea of the maximum tightness (clutch action) that can be achieved by hand effort alone. At this point,
you must bear in mind that for optimum performance all three C
LUTCH
K
NOBS
on each axis (R.A. or Dec.) should be
tightened evenly with the same tension (i.e. all three half tight, all three fully tight, etc.).
In order to feel the effect of the C
LUTCH
K
NOBS
, you may wish to assemble your mount with the mounting plate and
C
OUNTERWEIGHT
S
HAFT
. Do not put scope and C
OUNTERWEIGHTS
on at this stage. With the above assembly (with the
C
LUTCH
K
NOBS
firmly hand tightened - "as shipped"), you can feel the amount of force needed to move each axis by
hand. Grab each end of the telescope mounting plate and move it with a backward and forward movement of the
Dec. axis. You will feel considerable resistance to this motion. Perform the same operation on the R.A. axis by
moving the counterweight shaft backward and forward. With a well-balanced telescope, the above tightness of the
clutch knobs will be sufficient for all normal conditions of use.
Now, mount up and balance your telescope so you can "feel" what this resistance in R.A. and Dec. (movement
backwards and forwards) is like when you make these motions from the eyepiece end of your telescope as you
would during normal use when slewing (pushing) by hand to acquire an astronomical object within the field of view
of your finder or scope.
3. How tight can the clutch be and can you do any damage by over-tightening them?
These clutches can be tightened as much as needed. There is no danger of over-tightening. You will see that
each clutch knob has a 3/16 hex socket for tightening with an Allen key. Using the provided hex key you can lock
up the clutches so that only the worm drives are able to move each axis. You should
NOT
attempt to push your
scope by hand against this "locked up" resistance, or undue stress will be placed on the worm wheel, worm gear
and bearings.
Most users will never need to use a hex key on their
Mach1GTO
’s clutches, but if you are heavily loaded, if your
system is out of balance, or if you are doing critical long exposure astro-photography, you may wish to have the
extra clutch tightness. As a general rule, if you have a big scope (6" refractor or 10” SCT) with all the accessories,
you will need more clutch tension than a 4" or 5" scope.
Balancing Your Telescope
For proper operation, the telescope must be adequately balanced along both axes. Start by balancing the tube assembly.
First, Balance the Declination Axis.
1. Position the mount for balancing. Move the R.A. axis so that the C
OUNTERWEIGHT
S
HAFT
is pointing down. The
declination axis assembly will be in the meridian (this is the classic photographic pose for a German Equatorial).
Position the Dec. axis so the telescope tube is horizontal and pointing east.
2. Tighten the 3 R.A. axis C
LUTCH
K
NOBS
.
3. Loosen the 3 Dec. axis C
LUTCH
K
NOBS
(about 2 to 3 full turns) so that the telescope moves freely about the
declination axis. NOTE: because of a spring mechanism, you must loosen the knobs past where they begin to feel
loose. Be careful because if your telescope is significantly out of balance, it may swing rapidly in the out-of-
balance direction!
4. Loosen the tube mounting rings and slide the tube back and forth for balancing. This is best done with the tube in
the horizontal position. If you are using a dovetail mounting plate, slightly loosen the hand knobs on the female
dovetail receiver plate and slide the male sliding plate (and thus the telescope) to the desired position.
5. The scope is balanced when it
stays put
(does not move) with the clutches loose and movement back and forth
about the declination axis has the same feel in both directions. Be mindful of eyepieces, cameras and other
accessories that are yet to be added and compensate accordingly.
6. Re-tighten the telescope mounting rings or mounting plate dovetail clamps!
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Summary of Contents for Mach1GTO
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