NGC 6888, The Crescent Nebula

NGC 6888, The Crescent Nebula, LBN203, Magnitude 10.0, Size 10.0' x 10.0', Constellation: Cygnus

Image Details:

• Scope: 1995 Celestron Ultima 8 OTA.
• Mount: Celestron AS-GT (goto CG5).
• Camera: Meade DSI Color.
• Configuration: f/3.3 focal reducer, both spacers.
• Effective Focal Length: 609mm, f/3.
• Exposure:  40 images @30 seconds.
• Filter: Meade IR blocking filter.
• Acquisition: Meade Envisage.
• Guiding: None.
• Location: Deep South Regional Star Gaze, Camp Ruth Lee, near Clinton, Louisiana.
• Date: 30 October 2005.
• Post Processing: Meade IP.
• Photoshop: Unsharp Masking, Levels, JPG conversion.

Comments: The quoted magnitude value for this object, 10.0, is really a laugh. This is a very dim object; its actual surface brightness is a depressing 16. Surprisingly, it is actually quite doable visually from dark sites with scopes in the 11 - 12 inch aperture range--if they are equipped with an OIII or UHC filter. NGC 6888 is decidedly more challenging than the Veil Nebula. It is akin to it, however, in that it is more like a supernova remnant than a "normal" emission nebula. The Crescent appears to be made of the gas thrown off by a an evolved star near the center of its arc, a "Wolf-Rayet" star.

I was not sure whether the C8 and DSI would be up to the challenge of this dim semicircle of nebulosity, but they acquitted themselves very well, showing both detail in the nebula, and the very faint glowing gas on the inside of the arc.

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