Abell 21 (a.k.a. SH2-274) - The Medusa Nebula, a planetary nebula in Gemini.
This image is a color composite consisting of a stack of 5 eight minute exposures for the
luminance channel and each of the color channels.
A Hydrogen-α filter was used for acquiring the exposures for the luminance channel.
The images were acquired using an SBIG ST-10 CCD camera through a Tele Vue NP-101 101mm f/5.4 refractor.
The exposures were stacked and a Sigmoid Scaling of the luminance channel was performed.
The colors were joined and automatically balanced using AIP4WIN V2.2.0.
This image has been resampled from its original size of 2184x1472.