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Subject: Re: Long post on drive rates
From: Steven Williams
Reply To: mapug@shore.net
Date: Mon Apr 10 00:47:27 1995
On Sun, 9 Apr 1995 dicicco%cfa4.DECNET@cfa.harvard.edu wrote:
> Within a few minutes I could see that the scope was tracking fast
> (moving west of the star). But I let the test continue for nearly 4 hours.
I've been folowing this with interest. My Lx-200 displays a periodical error of 8 arc seconds. I too erased the PEC and found that no drift was noticeble both in alt/az or equatorial mode.
> The scope had moved 384 arc seconds (6.4 arc minutes) ahead of Sirius.
> Taken at face value this is about 1.75" of drift per minute, but not all
> of it is due to the scope -- refraction, especially near the end of the
> test, caused some of the displacement. Even so, the drift rate is still
> at least 1.5" per minute. This does seem high, but it confirms earlier
> suspicions I had when testing both Meade and Celestron PEC systems --
> namely that the drive rate was being affected by the PEC.
This is what I *can't* simulate. After training the PEC, I obtained about 4 (+/- 1") arc seconds periodical error but no drift that you and others have reported. I could only test this for about an hour, as we had cloud move in. The weather has been terrible in Australia of late (sigh).
I don't know if it's my particular model or not, but I will try and run this test again when I go up to the observatory later this month. I'll do some carefull testing and report to the list. I have a LX-200 10" f/10 system with 3.30L of the software.
Before anyone jumps in, YES, I know I'm lucky with the periodical error of my system, I'm also lucky that I can achieve a 1 arc minute acuracy with the HP on (on the stars that are acurate) when in alt/az mode. I haven't yet set my wedge EXACTLY to for any testing of accuracy in equatorial mode.
> Okay, so we have a limited test of two scopes that shows the PEC causes
> the scope to run a bit fast.
And one that doesn't (mine), strange....
Steven Williams - Managing Astronomer Grove Creek Observatory, Australia.
e-mail: stevew@gco.apana.org.au ftp: wwa.com:/pub/ccd WWW: http://gco.apana.org.au