Re: Adjust CP4 Clock Frequency

Roland Christen

Or C you are not polar aligned or D you have differential flex which I have seen in the larger SCTs in fact of this magnitude and more.
It is virtually impossible for the encoder to have such large errors- your error is off by 100x. I just ran a test of a random encoder mount, tracking at sidereal, counting pulses from a Renishaw encoder over time. The tracking rate is constant over a 30 minute period of less than 0.2 arc seconds. I then changed the tracking rate by 0.1% and recorded the error - I can upload an image showing the result if you don't believe it.

Roland Christen

-----Original Message-----
From: Craig Young <craig.young.m8@...>
Sent: Tue, May 5, 2020 7:33 pm
Subject: Re: [ap-gto] Adjust CP4 Clock Frequency

I disagree Ray that this is the more likely reason.  If it were the reason then I would see a divergence between ATrack and APCC.  I don't, they follow each other in parallel which means there is a constant factor that is causing the difference.  The two likely constants are: a) the sidereal rate is not sidereal, or b) the encoder, if used to determine sidereal rate, is not calibrated.


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