Elgin Observatory
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Telescope Drive

    This scope is controled by Mel Bartels' - Alt/Az Scope Driver

QUESTIONS AND ANSWERS
From: "SHAW, CHARLES W. (CHUCK) Do the belts have much hysteresis or backlash??? Since its a GEM the RA would always be pulling in the same direction, but what about the Dec axis?

I have not tried measuring the system errors, but Mel's backlash function should take out any problem hysteresis. The RA (AZ) is quite tight and I have not had any problems with it. The DEC (ALT) axis is sloppy, but since I don't track with the DEC axis, I have been satisfied to be able to get the object on the ccd chip. I do have encoders, and that helps in solving slippage problems on long slews

What did you use for gearboxes? They are nice and compact!

The RA gear is 100:1 worm box from Allied, if I remember right. Stock Drive Products, Sterling Instrument has a simillar "speed reducer". The DEC gear is a 1950s vintage Edmund sideral drive gear set that I cludged a mount for. A bit sloppy, but again I don't track on that axis.

From: "Aurigema, Andrew N" Where did you get the belts??? Are they kevlar re-enforced timing belts??? I assume they are smooth??? Drew in sunny Fl

I have had the system long enough to have tried several materials. Dan Gray of Portland OR has a "belt drive". He sent me samples of plastic coated steel fishing line. This works quite well, but a single pass over the drive pulleys did not provide enough friction. Looping the line around the pulleys works great, but in my case I did not have enough width on the drive pulley to allow the line to "walk" far enough for a full 180 degrees rotation of the scope axises. I finally settled on an ordinary clothes drier drive belt. They are plenty long, narrow enough to work well in this application and are smooth enough to give good tracking. The rubber friction face provides enough friction to do the job and they are strong enough to cinch down tight.


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