Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) 1.28 arcsec / pixel.  The Zoomify image scale is 1.28 to 3.33 arcsec / pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ internal filter wheel, AstroDon Filters

Acquisition Data

2/14/2010 to 3/12/2010 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.

Exposure

Lum (no filter) 375 min (25 x 15 min, bin 2x2)

RGB               225 min ( 5 x 15 min each, bin 2x2)

Software

• CCDSoft, CCDStack, Photoshop CS w/ the Fits Liberator plugin. Noel Carboni's actions.

• eXcalibrator for (b-v), (v-r) color calibration, using 9 stars from the NOMAD1 database.

• PixFix32 (pre-beta) to repair hot/cold pixels and column defects.

• CCDStack to calibrate, register, normalize, data reject, combine the sub exposures and LRGB color.

• PhotoShop for LLRGB combine &  on-linear stretching.

North is to the bottom.

The Medusa Nebula, also known as Abell 21 and Sharpless 274, is located in the constellation of Gemini, at a distance of about 1,500 light-years. Since the nebula can be seen with a 10-inch telescope, it's recent discovery date of 1955 is surprising.

Initially identified as a super nova remnant, Sh2-274 was reclassified as a planetary nebula in the early 1980's. This planetary nebula phase is the evolution end game of low mass stars similar to our Sun. As these stars transform from red giants to dwarf stars their outer layers are thrown into space, leaving behind a planetary nebula. Ultraviolet radiation, from the remaining hot dwarf star, powers the nebula's glow.