M15 / NGC 7078, globular cluster: der Kugelblitz*

*German "Ball Lightning".

 

It's a nice word and fits good here because of apparently saturated core. Technicaly it isn't, going only up to 230-235 8 bit values but looks like as it's about to explode ):

 

One of the most ancient globular clusters in Milky Way and surprisingly bright one.

 

Acquisition time (start of a session): JD2456865.33452546 (27.07.2014, 00:01:43 MSK)

Equipment:

Canon EOS 60D (unmodded) running Magic Lantern firmware override fitted with Baader Planetarium MPCC MkIII coma corrector on Celestron OMNI XLT 150 mm Newtonian riding on Skywatcher NEQ-6 Pro mount with counterweight shaft extention.

Aperture 150 mm

Focal length 750 mm

Tv = 30 seconds (the tracking was very loose and even just 30 seconds appeared too much)

Av = f/5

ISO 1600

Exposures: 50 of 170 (plus 72 dark frames plus 100 flats and respective master offset library).

Processing: Images were converted into .DNG and fed to DSS. Final touches were "creatively" done in Photoshop. The following was included

1) setting gamma to 2,75;

2) setting black level roughly 8-10 8-bit units below actual minimum;

3) applying highly assimmetric sigma-like curve (I tried to preserve at least some of little "fuzzie"s that got caught in this field);

4) fine-tuning the background to 1-2 8-bit units.

Note: it's the third image with the particular mess in the bottom right corner. What's going on?

Done