[AZ-Observing] Re: Gegenshein and a question
- From: "Steve Coe" <stevecoe@xxxxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Mon, 11 Feb 2008 15:57:33 -0700
Dean;
I am just starting to learn about how to use my Canon Xt. Once I find =
out
something I will let you know. I am hoping to get down to Starizona and =
get
some lessons from Scott.
Steve Coe
-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
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Sent: Monday, February 11, 2008 3:42 PM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Gegenshein and a question
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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