RE: ATM The Big Dob Two-Step (-per drive)

[andydtg@phoenix.net]

Chris W. wrote:

>What I have planed for a drive for my SST/Graphite scope is an engagable
roller drive system.   I would let hand guiding be done on Teflon on Formica
bearings, a la Obsession.  But I would cut a 1 cm wide track out of the
Formica, where a 1 cm wide SST roller bearing could mate with the SST
bearing.  A lever could engage all of the bearings (I figure7 in all .. 4
Alt, and 3 Az) at once, to convert to driven scope.  No compromise on the
feel or accuracy ... essentially you would get both high accuracy tracking,
but the ability to guide easily by hand.

The roller chain drive lets you do this without engage/disengage mechanisms
for visual only systems.

Sounds OK but I have some concerns about getting sufficient friction between the
SST rollers & tracks to drive the scope reliably. Also if you bump the scope
while
the drive is engaged you can damage the roller and/or the track by the sliding
contact: not significant for visual drives but disastrous for photo
tracking; not
to mention that if you're using Mel's encoderless system you'd have to realine
the scope each time it slipped.








Andy Saulietis / DTG Alt-Az-Fp Drive Systems
12617 Harriet Ln
Santa Fe, TX 77510 USA
409-925-8854 Voice/Fax