[AZ-Observing] Gegenshein and a question
- From: ketelsen@xxxxxxxxxxxxxx
- To: az-observing@xxxxxxxxxxxxx
- Date: Mon, 11 Feb 2008 15:41:58 -0700 (MST)
Hi All-
Steve Coe mentioned the other day how visible the Gegenshein was on the
weekend - I was having some backlash issues with my mount, so went to wide
field imaging. Unfortunately, I forgot my adaptor to use my Nikon lenses,
so I had my Canon zooms to use with the 20Da.
Anyway, one of my targets was the Gegenshein, and for it used the 10-22
Canon zoom at 10mm wide open at F/3.5. Cropped slightly, this is 4X3
minutes at an ISO of 1600:
http://alice.as.arizona.edu/~ketelsen/Gegenshein%204X3m.jpg
I'm really impressed with the sharpness of this lens - it is fun to cruise
around the frame at full resolution. There is a little vignetting and
that brings me to my question - how do you shoot flats with a lens with a
107 degree diagonal FOV? I usually shoot sky flats during twilight, but I
don't think the sky is uniform enough that wide. Any ideas?
BTW, here are a couple other shots - the winter Milky Way from south of
Canis Major to Comet Holmes and a little Zodiacal Light, here with 18
minutes total exposure:
http://alice.as.arizona.edu/~ketelsen/WinterMilkyWay%206X3m.jpg
Here a quick shot of the western sky after moonset about 2200 local time
with 9 minutes total exposure:
http://alice.as.arizona.edu/~ketelsen/West%203X3m.jpg
Thanks in advance for thoughts on flat fielding...
-Dean
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