This is the spectacular globular cluster called M3.
M3 was the first deep space object I tried to photograph with my current telescope and camera, about 5 years ago, and that first image can be seen for comparison at the bottom of this gallery.
I got a late start on this night and was only able to acquire 11 three minute exposures of the cluster, at ISO 800, before I had to stop as the object crossed the meridian to prevent the telescope from colliding with a tripod leg. Earlier in the night I had acquired 10 twenty second exposures to resolve the bright core, 16 flats and 16 flat darks, but I forgot to acquire dark frames on this night, the warmest of the year so far.
I processed the frames in Iris software, using flat, flat dark and bias frames, but without dark frames, and using a hot pixel map made about two weeks ago. I finished the image in Photoshop CS5, layering in the composited short exposure image of the core. The only significant effect I could see from the lack of dark frames was a substantial amp glow in the lower right corner, which I cropped out.
|Imaging telescope:|| ||8" f/4.9 newtonian reflector|
|Telescope mount:|| ||Atlas EQ-G|
|Mount control software:|| ||Cartes du Ciel, via EQMOD|
|Imaging camera:|| ||Canon EOS 350D|
|Guiding telescope:|| ||80mm f/11 achromatic refractor|
|Guiding camera:|| ||Meade DSI-C|
|Guiding software:|| ||PHD Guiding|
|Raw image processing software:|| ||Iris|
|Image finishing software|| ||Photoshop CS5|