M27 – Ha + O-III Bicolor
Telescope: Meade LXD75 SN6
Camera: Meade DSI Pro III
Guide scope: Meade DSX-90, PHD
Software: Envisage, Autostar Image Processing, Nebulosity, Photoshop
H-alpha: 20x120sec, Orion 7nm H-alpha Filter
O-III: 20x120sec, Orion 7nm O-III Filter
L = H-alpha + O-III
R = H-alpha
G = O-III
B = O-III + 20% H-alpha (synthetic H-beta)
To try my hand at bicolor imaging I wanted to start with something familiar and fairly bright. My goal for narrowband imaging is to make use of moonlit nights and to eventually go after targets that are tough from a red zone. I also want to try to process the images as close as I can to their proper color. This is really fun as while H-alpha (and S-II) is a nice red-red, O-III is right in the middle between blue and green. You can discriminate between the two though by blending in about 15-30% of the H-alpha with the O-III to simulate the H-beta line which lies a bit more towards the blue than the O-III line. Sooo, as a first hack, I’m pretty happy with the overall result.
The source images for M27 were really impressive as I was able to just barely see the faint outer shell, though I lost most of it in processing.
Just for yucks I went back and pushed the processing a bit harder. I generally shy away from this as I'm not very good at it and it starts to move from imaging to art, and I'm no artist. In this image I applied more agressive curves to the luminance and pulled the green channel down a bit. The teal color is actually more accurate, but I think this one is more colorful.