M57 - The Ring Nebula
The star which burned out and blew off this smoke ring is still visible in the center. NGC 6720 (known as the Ring Nebula and M57) is in the constellation Lyra (The Lyre). It has a magnitude of 9.0, and is 2.5 arc-minutes across. It is 2,000 light years away.
This shot is a composite of three 10 minute luminance, one 10 minute red, two 10 minute green, and two 10 minute blue frames. All frames were unbinned at f/10 with the 12" LX200 and ST-8E.
The AO7 adaptive optics unit was used to rapid guide on a magnitude 10.3 star just north of the field. Some frames were at 0.1 sec, some at 0.2 sec, and some at 2 sec. (I was experimenting.)
Processing included CCDsharp on the luminance, and "by the numbers" color calibration.
Taken on July 27, 2000 at my home in Monmouth.
This previous shot, taken a year earlier, was from the first evening in which I attempted color:
Built from a 2 minite red frame, 3 minute green frame and a 6 minute blue frame. Taken at f/6.3 with the 12" LX200 and 416XT through the Meade 616 filter wheel. Autoguided with a 201XT through a 90mm ETX.
Color was balanced by examining pictures of a G2 star, however it still seems a little red to me.
This shot was taken July 9, 1999 at ARGO.
The exposure below was taken Aug 10, 1997 in my front yard in Corvallis Oreon.
A 2 minute binned exposure taken with the 416
at f/6.3 in my front yard. The stars are slightly oval since I
had not yet trained my drive for periodic error correction