Service Note #5   Adjusting the Lens Carriage

Author:  Tom Droege            
Date:    Aug 19, 2002

The Dec. carriage can have problems moving if it is not well balanced.

The first thing to do is to loosen the two set screws that hold the Dec. 
axle.  The set screws are in a counter bored hole in the middle of the 
black bars that connect the Dec axle to the carriage.  You should now be 
able to push the carriage around freely, balance it, and find where it is 
hitting something.  Of course remove the clamp while doing this.  Note that 
these screws do not grab the axle very well.  So the carriage has to be 
well balanced or it will slip.  This is just as well, since the Dec motor 
is delicate, and will probably break if it tries to drive through and 
obstruction.

To balance the carriage, the easiest thing to do is to move the 
lenses.  First you get the camera focused.  Then you measure the focus 
position.  I do this with a caliper.  OK, now you know the spacing between 
the end of the lens and the camera.  You need to hold this constant while 
the lenses are slid in and out until a balance is found.  Just loosen the 
big hose clamps on the telescope tubes to do this.

Once you find a balance that you like, then you will want to move the stops 
so that the focus is not to far away from the stop.  Say .1 or .2 inches 
away from the stop.  This give you room to focus while not taking so long 
to go in to the stop and back out to the focus position.

Note that the whole carriage can be slid along the axleel.  This allows 
positioning the brake disk far enough away from the brake pad that it does 
not rub, and close enough that the brake clamp can grab it easily.  If the 
carriage is well balanced, then one can turn off the Dec drive motor 
without it moving.  If it moves, then you probably want to change out the 
Dec motor for the high gear ratio version, or work harder on the carriage 
balance and the free motion of the tubes and cables.