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Old 05-09-2011, 10:07 PM
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alistairsam
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alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
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Hi,

I understand the difference between angular units and the time based equatorial units. just stated that for context.

Quote:
Originally Posted by bojan View Post
That is why I think that for good closed loop system you need the encoder with such accuracy and resolution (1 arcsec or better, directly on the RA shaft - and this is very expensive encoder).
Or, you can have encoder on the motor shaft, but the subsequent PE must be compensated somehow.. and the most efficient way is auto guiding.
Is this even possible? I'm guessing these are not optical.

I have three gear reduction stages, two of which are timing pulleys and one which is a mclennan spur gearhead.
I might drive the encoder from the input of the final stage instead of the RA shaft as the backlash with the timing belt/pulley would be minimal when tensioned correctly.
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