Re: [APML] A question for you ST-4 experts

["Mike Connors" <micon@starband.net>]

Hi Alan,

Employing Ron Wodaski's 'CCD Calculator', at 820mm focal length, 
it's about 660 arc-seconds field of view across the ST-4 chip, which
roughly translates to 44 seconds at sidereal rate.  So, your calibration
time seems like it should work.

With a guidescope of 900mm focal length, and a 15-second run,
I typically get 0s and 1s with an occasional 2.  That's OK for me, so
I haven't tried to improve it.  Doesn't seem to me that it gets much
better, but who knows?  
  
Increasing the calibration time ---might--- improve performance,
by yielding a more accurate figure for pixels/second.  It's something
of a no-lose situation: it can't hurt to try.

Maybe you've seen this write-up:
http://acp4.dc3.com/McMillanAutoguiding02-2005.pdf
A good 'guide' to one man's cumulative experience on autoguiding.



HTH,

Mike Connors


----- Original Message ----- 
From: "Alan Voetsch" <alanv12952@yahoo.com>
To: "APML" <astro-photo@seds.org>
Sent: Thursday, August 25, 2005 10:01 PM
Subject: [APML] A question for you ST-4 experts


> Hey all,
> 
> I've got an autoguider calibration question I want to lay on you guys.
> 
> First, some history. I've used the Meade 201XT (Rich Michaels; where
> are you now?) on my LXs for quite awhile. There has been past
> discussion that increasing the calibration numbers will result in
> better, smoother guiding. I tried this, and it worked on the 201 and
> LX200 mount. Somewhere in the MAPUG archives is an article I submitted
> regarding this issue. Ralph Pass is the one who originally suggested
> doing this, it also worked for him.
> 
> I wonder if this is worth pursuing on the ST-4 and G-11. Has anyone
> checked this out and were there any results worth mentioning? I
> currently start calibration with the star roughly centered and use '20'
> for calibration numbers at 820mm focal length. That moves the star to
> about '75' and '15'. If I started with the star at '15' and '85', I
> could use '40' as the calibration entry and keep the star on the chip,
> and have twice the movement during calibration. Hopefully, this would
> improve guiding performance.
> 
> OK, any insights at all out there?
> 
> Thanks,
> Alan
> 
> SCT Astrophotography: http://www.pbase.com/avoetsch/astrophotography
> FS-102 G-11/Gemini: http://www.pbase.com/avoetsch12952/tak_fs102
> & http://www.pbase.com/avoetsch12952/fs102
> & http://www.pbase.com/avoetsch12952/takpf
> 
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