Re: [APML]: LX-50-astrophotography? & ST-4 test first night

[cvedeler@bio2.edu (Chris Vedeler)]

The Astro-Photography Mailing List
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At 09:58 AM 7/28/98 -0400, you wrote:
<snip>
>
>I am using a refractor to guide the SCT for now, primarily as a tool
>to work out the ST4 issues.  My results from last week showed guiding
>errors, but not mirror flop.  I do have a GEG, and if I'm able to
>work out the issues with the LX50 mount, I'll move to installing the
>ST4 on the GEG.  I have constructed a mirror lock down tool, a la
>Chris Vedeler, and would also use this.  In any case, I'm not
>tracking across the meridian, and use shorter exposures (30-45 minutes)
>on brighter objects.  In guiding manually, I've not noticed mirror
>flop in exposures of this length.
>
>Thanks for the suggestions so far, this is definitely a learning
>experience.
>
>-- Gil
>

If your guidescope mount is very, very ridged and well mounted to your SCT
AND you lock the mirror down you can probably get away with 30 minute
exposures most of the time, 45 minute exposures maybe half the time and hour
long exposures essentially never.  Some of my best shots where done using my
guidescope and 30 minute exposures.  I'm not using it much anymore however,
since learning how to make my GEG work with an autoguider.  Sometimes I
think about putting the guidescope back on for those shots of brighter
objects since setup was so much easier.  But I think of the GEG as
insurance.  It's a much bigger pain to get a guide star than with a
guidescope, but once you get it, you know your guiding at least will be
nearly perfect.

Chris Vedeler
http://www.isomedia.com/homes/cvedeler/space.htm
Tucson, AZ

PS:  Take a look at one of my first attmepts at real CCD imaging with my
ST-7.  It's a 8 minute exposure of M17.  Any ideas what the black centers
are in some of those stars?  I'm guessing the focus was a little off.
http://www.isomedia.com/homes/cvedeler/m17ccd.jpg