M57, The Ring (Planetary) Nebula

M57, NGC 6720, Magnitude 9.40, Size 1.4' x 1', Constellation: Lyra

Image Details:

• Scope: 1995 Celestron Ultima 8 OTA.
• Mount: Celestron AS-GT (goto CG5).
• Camera: Meade DSI Color.
• Configuration: f/6.3 with Celestron Reducer/Corrector.
• Effective Focal Length: 1279mm.
• Exposure:  20 images @15 seconds.
• Filter: None.
• Acquisition: Meade Envisage. Quality = 0%.
• Guiding: None.
• Location: Pine Lake Observatory, Mobile, Alabama.
• Date: 4 June 2005.
• Post Processing: Meade IP.
• Photoshop: Unsharp Masking, Levels, JPG conversion.

I think M27 is a "better" planetary nebula for the amateur, but I know The Ring is very much beloved. In addition to the fact that it's so bright that almost any scope of more than 3 inches of aperture will show its ghostly smoke ring, there's always The Quest. For the Central Star, that is. The progenitor of the Ring,, a desiccated white dwarf, is at magnitude 15 or WORSE, is possibly variable, and is made all the harder by the fact that The Ring's center is full of hazy nebulosity. This donut is a filled donut, you see. Nevertheless, I've glimpsed the sucker with a 12 inch from a dark site at very high magnification 600x plus (high magnification helps spread out the interior nebulosity...you'll obviously need good seeing for this technique to work).

How far away is The Ring? Like most planetaries, the distance to this one is not well known. Maybe 2000 light years. Is it really a ring? Probably not. Astronomers used to think it was a hollow bubble or shell, with the ring shape produced by thicker gas at the limb. It is now, however, thought to be a (mostly) hollow tube of nebulosity.

What did I do wrong with this very early DSI image? More like what did I do right? I threw out the color information because I had no idea how to process a color DSI image and kept winding up with florescent green Rings. I got some star trailing because I thought setting the quality factor on Envisage to 0% would help. I didn't see why I couldn't leave the IR blocking filter out. Sigh. Ah well, there's always next year. It is amazing how easily the central star shows up with such a short, misguided (in more ways than one) exposure...

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