another look at M27, always fun to process. this image is my best example of the blue-green color from ionized oxygen..
a combination of 7 x 300 second subs at f10 and 24 x 60 second subs at f5.9. The two sets were acquired and combined separately in Nebulosity and curved in Photoshop CS3.
The two sets were then resized, aligned, and combined in Photoshop CS3. A bit of soft-light>hi-pass sharpening was applied to each before combining
and a final soft-light>invert>hi-pass softening was given the highlights after an overall Noise Ninja at 50%...

to note, the shorter exposures were much bluer, the green cast only came in with the longer subs.... color is default de beyer (modified IR) in Nebulosity.

12- inch LX 200 at f10 and f5.9, giided with PHD and a dsi pro on an old 80mm Meade f11.
sky transparency good, stability average, a bit soft for the longer exposures making fat stars, moist September 5, 2007, Julian CA