M27 / NGC 6853, planetary nebula: Another famous apple core

Had slipped between the clouds and escaped the flood of dew to bag my second planetary nebula - the (apparently) largest one of their kind in the sky.

 

Acquisition time (start of a session): JD2456900.288843 (30.07.2014, 22:55:56 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 & 60 seconds

Av = f/5

ISO 1600

Guiding*: QHY5L-IIm on 50 mm f/3,8 "DeepSky"-branded mini-guider, serviced by PHD Guiding ("Push Here Dummy" :)

Exposures: 35x30 sec of 7x60sec (plus 32 and 13 respective dark frames plus and respective master offset and master bias from the library. "Light" frames were inspected and the best were manually and visually preselected basing on the roundness of the stars and abscence of clouds).

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;

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

5) extra step: color balance was slightly touched to remove overall redness of the stars.

 

*Noted solely to indicate the fact that the guider was attached and operating :)

 

Upd 02.09.2014: I have replaced the original image with one processed in better lighting conditions.

Done