Re: [APML] NGC 6992 uploaded

[Ray Butler <ray.butler@nuigalway.ie>]

Hi Alan,

Stuart & Gary have addressed the image processing aspects. I think that 
their advice will really bring out the great potential in your image 
data. But I have something else to add, which may help your results in 
general.

I notice 3 things:

1) You do not use a field-flattener (the field edges have some field 
curvature & astigmatism)
2) You use an off-axis guiding setup & an ST4 guide CCD
3) The image has some slight trailing, so the autoguiding didn't work 
perfectly.

I think that these 3 things may be related. Without a field flattener, 
the off-axis autoguider has to work with bloated, aberrated stars 
off-axis, and this may explain why it trailed a little.

So not only might a field flattener make the image more uniformly sharp, 
it might also help with guiding. I'm sure that Tak have a dedicated 
flattener for the FS102. Just something to look into.

Ray "who thinks that this is one case where 'throwing more money at the 
problem' might actually help" Butler

Alan Voetsch wrote:

>All,
>
>Hate to drop another dud on you guys, but I don't know where to go with
>this next. Believe it or not, I think the BG is too dark, especially
>now that I was able to run the Adobe gamma routine. With over 6 hours
>total exposure on 2 different films, I expected more. I suspect that
>I'll be staring over again (from scratch) on this one. Take a look and
>let me know of any advice or suggestions. 
>
>http://www.pbase.com/image/34110658
>
>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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-- 
Dr. Ray Butler
Lecturer, Physics Department & Computational Astrophysics Laboratory,
National University of Ireland - Galway, 
University Road, Galway, Ireland. 
Web: www.nuigalway.ie/physics/ 	Email: ray.butler-AT-nuigalway.ie 
Tel: +353-91-493788 		FAX: +353-91-494584

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