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This nebula contains all 3 of the target spectral lines, hydrogen-alpha, sulphur-2, and oxygen-3. But I didn’t get enough OIII data to do anything other than balance the color of the stars. I was using 8 minute sub-exposures because that’s where bright stars were starting to saturate, but I think I would need to go to longer subs to get any OIII nebulosity. The SII image has significant nebulosity, but not a lot of differentiation from the H-a image, so longer subs would probably help there as well.
This is a 2×1 mosaic and, unusually, doubles the longer axis. Not many targets are as elongated as the California Nebula.
The channel assignments are R=H-a, G=SII, B=OIII. However, I tweaked the hue slightly after combining the channels because this shows the difference between H-a and SII more clearly.
Guiding was excellent most of the time, but the wind seemed to affect it at times.
Scope: AT111EDT at f/5.6
Mount: AP Mach1
Camera: QSI 583 at –25C
Exposure: 10 x 480s H-a, 10 x 480s S-2, 6 X 480s O-3 (2x each for mosaic) (7 hrs total)