M56 with C8, 9x100s, Calibration, Stack and Process

M56 is a globular cluster of magnitude 8.3 in the constellation of Lyra.  It's about 33,000 light years distant.  This is compared a magnitude of 5.9 for M13, that I have imaged a few times before, hence the greater difficulty in getting quality data. I had to reprocess multiple times as the flat frames didn't get rid of the dust donuts on the optics. They are still visible, which means my optics must be filthy.  This was probably all picked up during my excursion to Worcestershire a couple of weeks ago. I'm still not very happy with the result, but there was more mist in the air than was visible when capturing, and this drastically reduced the number of images available to stack.  This image is composed of 9 x 100 seconds exposures.  Out of a total of 37 subs, having only 9 barely usable ones is a bit disappointing - there were also many that were out of focus at the edges.  This is partly due to the big drop in temperature during the data capture (although I did auto-focus with FocusMax beforehand), and compounded by the fact the telescope needs collimating. I cropped and stretched the data in MaximDL, and then adjusted levels, curves, saturation, Gaussian blurred, and despeckled in Photoshop.