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RE: [APML] NGC 7789 posted
Hey Scott,
--- Scott Hammonds <shammonds@creatorsview.com> wrote:
> Just out of curiosity, how much moisture is in the air and are you
> using nitrogen or dry air for a purge?
There's not much this time of year. Haven't seen any dew for a couple
months. RH will sometimes climb to 60-70% by the early morning hours
and is usually around 15-20% in the late afternoon. No purging.
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.
There are several things it could be, at this point I'm prepared to
call it a guiding fluke. The stars are not exactly elongated all the
same, but it's close. After blowing up some other recent images, I
believe the elongation here is more the exception than the rule. Bill
has been kind enough to mention some things that I may have been
getting complacent about. The scope is in an observatory and
permanently aligned, therefore it hasn't been touched in several
months. I need to check all my connections including lock down screws
on the Taurus.
The other strong possibility is negative bowing. This inage came from a
strip that I did not have time to get mounted and so it was scanned as
a strip. Thar usually causes bowing. In that case though the stars
usually point back to the center of the negative. Although, that
doesn't appear to be the case here, it may be one of several
contributing factors.
> The image looks pretty good, glad you are getting some clear skies.
Me too after the lousy spring we had up here.
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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