[AZ-Observing] Re: Comparison of M78 LRGB Vs Hydrogen Alpha

I like how that gray nebula in the middle is just black in the Ha
picture. 

Does this mean it is a foreground reflection nebula that looks like a
dark nebula since it is knocked way down by the Ha filter? Or is it
an emission nebula that doesn't emit at all in Ha?

Or a combination of dust and gas that doesn't emit in Ha AND obscures
the stuff behind it when imaged at Ha?

Joe Larkin 

--- Jon Christensen <jonc97@xxxxxxx> wrote:

> 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
> --
> See message header for info on list archives or unsubscribing, and
> please 
> send personal replies to the author, not the list.
> 
> 


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