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Don Reed | all galleries >> Galleries >> Astrophotography > Globular Cluster M3
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28-APR-2012 Don Reed

Globular Cluster M3

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

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