Saturday night was very clear and dry down here near San Diego, but quite windy...
I gave up trying to image at long focal lengths because of the wind, and instead started a wide-field image appropriate to Galaxy season.
The image is of the portion of Markarian's Chain in Virgo, just poking into Coma a bit (with NGC 4473).
I used my little Takahashi FS60C with a focal reducer for a 264mm focal length, a StarlightXpress HX916 camera, and 38 minutes of exposure unfiltered (I shot 60 minutes, but had to throw away a few 'cause of windblown trailed stars!), piggybacked on a C8 SCT, all carried on an AP900GTO mount unguided.
(the images are 1300x1030 in size, and about 175k)
http://www.lefevre.darkhorizons.org/ccdimaging/mkchn1.jpg straight image
http://www.lefevre.darkhorizons.org/ccdimaging/mkchn1lb.jpg labeled version
(North is down in the images)
I'm amazed at how deep the image goes for just 38 minutes exposure. The faintest galaxies I can easily pick out are mag 16.4, and the faintest star I can positively identify is mag 21.3. If I hadn't been shooting into my southern light-pollution gradient from my backyard, and had to throw away 22 minutes, it would probably be much deeper. It's quite fun to shoot an image like this, then track down all the visible objects. Incidentally, in making the labelled version, I had to check multiple references because of some conflicting positions -- in the process, I verified that the Coma/Virgo cluster charts in the Spring "Night Sky Observer's Guide" (specifically page 94, Volume 2) have a number of mis-named NGC and IC galaxies. The labels on the image are as correct as I can be sure of, verified through The Sky and SkyMap Pro along with some Palomar Sky Survey images from the web. The NSOG were generated with a version of MegaStar (it doesn't say which one), which leads me to believe that MegaStar must also have some mis-named galaxies in the region.
I'm going to make the image negative (makes it easier to discern really faint stuff) and try to chase down some of the really faint galaxies in the image. I'll post up that version later if anyone's interested.
Paul
