M20 - The Trifid Nebula


Also known as NGC 6514, this emission nebula (red) surrounded by reflection nebula (blue) is found in the constellation Sagittarius (the Archer). It has a magnitude of 6.3 and a size of 29.0 arc-minutes.  It sits at a distance of about 5000 light years.

The above image is an LRGB composite taken at f/6.3 on the 12" LX200 and ST-8E.  Ten 1 minute 2x2 binned luminance, seven 1 minute 2x2 binned red, seven 1 minute 2x2 binned green, nine 1 minute 2x2 binned blue, ten 1 minute 3x3 binned blue.  All exposures were unguided.

Color balance was tricky.  At a sky altitude of 23, extinction gives ratios of 1.00 : 1.13 : 1.25.  My CCD color sensitivity requires a ratio of 1.00 : 0.88 : 1.82.  The result is 1.00 : 0.99 : 2.28.

Taken at the ARGO site on 7/1/2000.

Previous color attempt:

This is an LRGB image.  The Trifid is the reddish area at the bottom.  The original intent was a color mosaic.  It was never finished because the color data seemed too crummy.  However the test shot with no filters was OK, so I later merged the crummy RGB in by doing an aggressive low pass filter on it, but leaving the test shot alone as the luminance data.

L, R and G are all 2 minutes. B is 3 two minute shots.  All were at f/6.3 with the 12" LX200 and Meade 416XT.  August 13, 1999 at the Table Mountain Star Party.

Aug 28, 1997 at the 1997 Oregon Star Party

On the first night of the OSP everyone around me seemed to be looking at this object so I figured I'd give it a go. The next night I studied the Trifid visually, and compared it to a view in a 20" Dobsonian. The Dob was brighter (Duh), but the 12" held its own in contrast and detail.

A 20 second exposure taken with the 416 at f/3.3.