[APML] Declination Drive problem

["William R. Mattil" <wrmattil@ix.netcom.com>]

Gentlemen,

While probably Off-Topic I have a problem when guiding photographs that
has me stumped. Situation is this, mount is a 1.5 inch shaft GEM with
conventional RA drive and tangent-arm Dec driven by a Hurst 1 rpm motor.
After being inspired by what I am seeing by lurking here I am trying to
refine my guiding and have run into this. By definition I was told that
tangent-arm Dec systems have "no backlash" and this seems plausable. But
what I am experiencing seems to be just that. Backlash. When reversing
directions there is a definent delay before the Dec reverses direction.
After disassembling the Dec assembly and drive I have come to the
conclusion that the "backlash" is present in the motor itself. Not the
drive assembly itself. So I pondered this and cannot fathom a solution.
I have three of these motors and they all exhibit the exact same
behavior. I would imagine that constructing a new motor assembly would
bear no fruit either since after adding the gears to reduce the speed to
1 rpm the backlash is introduced. That and the motor coasting. Can
anyone point me in the right direction here ? I can guide in RA with
*no* trouble at all, but this Dec thing is giving me fits.

Perhaps superflouous information would be:

10" f/6 Newt. Guidescope is 90mm f/11 refractor. I am guiding at ~303x
9mm EP and 3X barlow. Flexure is *not* a problem.

Trying desperately to get pin point stars .....

Regards

Bill
-- 
William R. Mattil	| Fred Astaire wasn't so great.
wrmattil@ix.netcom.com	| Ginger had to do it all backwards
(972) 399-4106		| and... in high heels.

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