RE: [APML] Observatory - the Mounting

[astropix@att.net]

 Chris wrote:

> Geoff, my tangent arm is a 3/8 threaded rod driven by the 3 inch spur gear.
> A dc motor has a small 1/2 inch spur on it to make it turn.  So the
> reduction is great.

 Chris... if backlash in the driven nut is any concern here... I've got an idea 
proven in other applications... spring loaded split-nuts. I can probably find a 
web-page with the generic part description/picture... let me know if you're 
intrested. I've played with this design for controling backlash and it works 
great! I'm surprised no one else is using it... it's common in many industrial 
motion transfer systems where zero backlash is required. 

> Another point of interest is the use of 60hz synchronous motors for
> the Ra drive.  Im tired of fighting the stepper motor vibrations that have
> plagued my AP1200 mount, and ruined more than a few ccd images.

 Agreed! While my actual experience is limited... compared to yours... my own 
research has convinced me that AC synchronous is the most precise and reliable 
RA drive. Even though my 1" wide RA wheel was intented for slewing... I'll just 
position it by hand and use good ol' 110VAC for the finite motion!

 Looking forward to your images...

 Geoff





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