[AZ-Observing] Re: Comparison of M78 LRGB Vs Hydrogen Alpha
- From: Joe Larkin <joeclarkin@xxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Sat, 14 Jan 2006 10:09:44 -0800 (PST)
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
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>
>
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