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The Jellyfish Nebula (IC 443 or Sharpless 248) is a supernova remnant in the constellation Gemini. This is a narrowband image consisting of 11 hours of exposure through H-alpha, S-II, and O-III filters with an AT65EDQ refractor. Instead of the usual Hubble "SHO" palette (S=red, H=green, O=blue), for this image I decided to use the HSO palette, with H=red, S=green, O=blue. The reason for this choice is the contrasting character of the Jellyfish itself (located in the lower right of the picture) and the unrelated nebulosity at the upper left. The Jellyfish glows strongly at both H-alpha and S-II wavelengths, hence its gold color, with a little O-II emission at the top and right edges where the blues can be seen. By contrast, the nebulae in the upper left emit mostly hydrogen. With the HSO palette this region becomes colored red, which I thought was aesthetically more pleasing than the green that results from using the SHO palette.

The red nebulosity is the edge of Sharpless 249, a large nebula that extends outside the frame. Surrounding magnitude-7 star 12 Geminorum near the top of the picture is reflection nebula vdB 75. To its upper right is ear-shaped nebula DG 99. The bright star to the right of the Jellyfish is Eta Geminorum (mag. 3.3).