Posted in Astrophoto Log on September 10th, 2008 by Northwest Astro
It seems like a rite of passage, as nearly everyone’s first deep sky image is of the Great Cluster in Hercules. It is bright, and you can take good images in under 30 seconds so you don’t need to put a wedge on your tripod to take the picture. At least as long as your stacking software can handle rotation + translation between images.
Half-Moon
Before we went out front to do any observing though, I managed to get a few shots in RAW of the half-moon. One of them turned out to be pretty good. 1/200 second exposure at ISO 100 with the focal reducer. Having a hard time getting focus and I am starting to suspect the focal reducer might be involved.
So after we got the scope set up out front, I showed him a few objects, like Jupiter, M13, M57, the usual starters in the summer sky. Unfortunately the level of light pollution makes visual observing of galaxies fairly difficult. Later on we were looking at the Double Cluster in the f/5 focal reducer and noticing how one cluster looks pretty average, while the other has 3 bright red stars in it. He commented “You should photograph this.”
Draft
Processed
So, I hooked up the DSLR to the scope for deep sky for the first time and tried taking shots of the Double Cluster with the focal reducer in place. Everything seemed curved and stars ‘blown out’ (loops of unfocused light flaring out from the star). Removing the focal reducer, I pointed it at M13 instead and took 50 exposures over about 30-40 minutes. The best 13 frames make the two images you see below.
The one on the left is a little unprocessed, and you can easily make out the skyglow from the moon and light pollution. The one on the right has been processed to try to darken the background as best as possible without using a mask, as well as try to bring out some of the color differences in the stars. M13 is a mix of yellow and blue stars, and I wanted to make that obvious to someone looking at the image.
