M20 (The Trifid Nebula)

M20, NGC 6514, Magnitude 6.30, Size 28.0' x 28.0', Constellation: Sagittarius

Image Details:

• Scope: 1995 Celestron Ultima 8 OTA.
• Mount: Celestron AS-GT (goto CG5).
• Camera: Meade DSI Color.
• Configuration: f/3.3 focal reducer, no spacers, visual back/1.25" nosepiece.
• Effective Focal Length: 812mm, f/4 approximately.
• Exposure:  20 images @30 seconds.
• Filter: Meade IR blocking filter.
• Acquisition: Meade Envisage. Quality = 30%.
• Guiding: None.
• Location: Stargate Observatory, Fairhope, Alabama
• Date: 2 July 2005.
• Post Processing: Meade IP.
• Photoshop: Levels, unsharp mask, color balancing, .jpg conversion, star size reduction.

M20 is a bit frustrating. It's easy to see and detect the three dark lanes that give it its "Trifid" appearance from dark sites. Under good skies with a C11, I can even see that the blue reflection nebulosity component is a different shade of gray compared to the pink/red emission portion. Light pollution doesn't seem to hurt the nebula much when it comes to CCDing either. But visually? Sky glow ruins it, and a nebula filter won't do anything for the rich, blue reflection portions. In the suburbs, it's often just a barely detectable haze. Even if the nebula is invisible or nearly so, you will at least get to see the open cluster associated with the Trifid.

M20, given its Trifid moniker by Sir William Herschel, is an emission nebula much like the nearby Lagoon, which lies a degree and a half to the south-southeast. This complex of nebulosity may or may not be a part of the Lagoon HII region--depending on whose distance estimate you rely upon. It is, perhaps, about 6000 light years away.

While the skies of Fairhope are now fairly compromised, I didn't have any trouble doing M20, even in the presence of passing clouds and haze. Color balancing was fairly easy, since I was able to use the blue section, whose shade was easy to get right, as a reference. I do want to come back to this next summer, as I've got a much better idea of how to use the DSI now than I did in June of 2005. At the time I took this shot, I'd only been able to use the camera once on the deep sky due to lousy winter and early spring weather (I got the DSI in November of 2004).

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