The Trifid Nebula is an extremely colorful combination of a reflection nebula and an emission nebula. The lower, reddish part of the nebula contains the emission nebula - hydrogren gas which is emitting red hydrogen light since it is being heated by the hot young stars within the nebula. The upper blue portion of the Trifid is a reflection nebula - it consists of dust particles that are reflecting the light from the hot stars contained within the emission nebula. Because the hot stars are mostly blue, we see the reflection nebula as having a blue hue.

In this image, North is Up. This image is cropped to 74% of the original full frame.

Exposure Details
Lens	Celestron C-8 SCT with Lumicon telecompressor
Focal Length	1100mm
Focal Ratio	f/5.5
Mount	Schaefer GEM - 7 1/2
Guiding	80mm f/11 guidescope with PHD Guiding
Camera	Canon 20Da
Exposure	104 subexposures of 180 seconds each at ISO 800- over 5 hours total exposure
Calibration	30 darks, 30 flats, 30 bias
Date	July 25, July 31, August 2, and August 3, 2011
Temperature	61F on 7/25, 68F on 7/31, 65F on 8/2, 59F on 8/3
SQM Reading
Seeing	4 of 5 on 7/25, 2 of 5 on 7/31, 3 of 5 on 8/2, and 2 of 5 on 8/3
Location	Pine Mountain Club, California
Software Used	Images Plus 4.0 for camera control, calibration, stacking and digital development and multiresolution smoothing. Photoshop CS5 used for curves and levels, saturation adjustments, high pass fitler, noise reuction, and star shrinking. Carboni Actions for saturation adjustments and additional noise reduction. HLVG for additional color correction.
Notes	M20 is a bit difficult to photograph, in that it is very low in the sky. Consequently, seeing effects are magnified since I'm photographing through thicker atmosphere. Nonetheless, this image came out rather well, and I was able to tweak some very nice colors out of it.