FreeLists / az-observing / [AZ-Observing] Comparison of M78 LRGB Vs Hydrogen Alpha

["Jon Christensen" <jonc97@xxxxxxx>]

I posted this to the SBIG list a while back but I thought it would be of 
interest to you folks.  
Peter Erdman shot a photo of M78 and vicinity in Hydrogen Alpha and noted how 
completely different it looked than my LRGB version.  Hydrogen Alpha filters 
filter out all but a narrow band of light at about 656 nm which is in the red 
spectrum and is associated with glowing hydrogen.  LRGB pictures are made by 
using clear, red, green and blue filters to try to approximate what the human 
eye could see if it could accumulate light as efficiently as a CCD camera.  I 
made a mouseover comparison of both images:

http://members.cox.net/jonc95/M78compare/m78.htm



The Hydrogen Alpha filter filters out much of the blue reflection nebulosity of 
the main nebula, and brings out interesting swirly patterns in the gas not 
visible in the LRGB version.  A lot of people mix LRGB and Hydrogen alpha 
photos to try to get the best of both in their pictures, but some think what 
you lose in the process is not worth it.

Jon Christensen
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