Viewing Notes
December 3, 2005
Marana, AZObsession 25" f/5 Dobsonian Reflector
I went over to Kent Patterson's to do some viewing and astrophotography using the 25" Obsession. I made some truss tube poles that are 1 inch shorter than the original truss tubes, but it turns out that I will have to cut another 3/4" off of the length in order to reach the focal plane of the Canon EOS 20Da. So I will have to wait until the next viewing opportunity to do some astrophotography using the 25" Obsession.
Kent was also having his own equipment frustrations because his new Astro-Physics 1200 GTO mount turned out too be more of a power hog than anticipated -- proving to be too much for two different deep cycle marine batteries on 10 amp circuits. So Kent got to play around with his 6" Astro-Physics refractor without GoTo or tracking. The views through that refractor were still pretty awesome, even if we did have to hand track the scope at higher magnifications. It would have been great to get an image or two with the 20Da, but there just wasn't going to be any prime focus astrophotography during this viewing session.
I did take a star trail image that turned out pretty nice. This is exposure has the following details: Canon EOS 20Da with 24-70mm EF lens at 35mm, 20 minute exposure at f/5.6, ISO 400, no noise reduction. The only post image processing done was to add the copyright notice and to reduce the file size to make this easier to view on the web page.
The mountains are illuminated by the skyglow from Tucson which is about 15 miles south of the observing site. Here is a picture looking south (same set-up as above except exposure time was 30 seconds and the focal length of the lens 24mm):
