RE: [APML] NGC 7789 posted

["Scott Hammonds" <shammonds@creatorsview.com>]

Alan,
Just out of curiosity, how much moisture is in the air and are you using
nitrogen or dry air for a purge? I didn't look closely at the image, but if
it is in all 4 corners, I'd lean towards film creep if you have high
humidity where you live. 

The image looks pretty good, glad you are getting some clear skies.
Scott 

-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
Behalf Of Alan Voetsch
Sent: Saturday, July 23, 2005 6:21 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] NGC 7789 posted

Hey Bill,

Yes I've noticed the elongated stars also. I haven't paid a whole lot
of attention to that problem because right now I'm more concerned with
getting the processing at least partly right. Maybe the mount is about
ready for another alignment touchup. At the very least I will double
check all my possible flexure points. At worst, maybe it's time for a
gear mesh adjustment as the G-11 is almost 2 years old. If that's the
case you'll probably hear me asking for advice on the Losmandy group.
8-)

Yes I do get occaisonal POP shadowing, darn it. 

Now you've given me more to keep an eye out for.

Thanks,
Alan

--- "William R. Mattil" <wrmattil@ix.netcom.com> wrote:

> 1) Your Refractor isn't up to the task ( doubtful IMHO)
> 
> 2) Polar Alignment problems
> 
> 3) Guiding Problems
> 
> 4) Flexure or other unwanted movement.
> 
> 
> My reason for mentioning this is that when I look at your "Raw" image
> 
> and look at the four corners I am not seeing  round stars. In fact if
> I 
> didn't know better I would be thinking that you were using a
> Newtonian 
> and have some coma. Furthermore this aberration is not equal in all
> four 
> corners. This same phenomenon is visible in the center of the image
> as 
> well but to a lesser extent. I am confused by this as Refractors =
> Round 
> stars (or so I always thought) so ....... maybe polar alignment ?
> Since 
> you are guiding off-axis one would think that it's not flexure but it
> 
> could still be differntial flexure between the film plane and the 
> guiding head.
> 
> Is there a slight shadow in the lower right caused by the pick-off
> mirror ?
> 
> Good processing and I like the framing of the object of interest.
> 



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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