Re: [APML] Blue in Packman nebula, real or not?

[Ray Butler <ray.butler@nuigalway.ie>]

Hi Joe,

I also think that it is real. But I don't attribute it to the H-beta and 
OIII lines that some people have suggested. There is also an OII 
emission line in the near-UV at 373nm, as well as H-gamma, H-delta and 
H-epsilon between ~390-430nm in the violet (which Dean's response 
referred to), all of which are registered by colour films on their 
blue-sensitive layer. This blue, added to the H-alpha red, is what makes 
highly-excited nebulae like M42 look "pink" rather than red, in 
unfiltered colour film shots.

If you see photos of M42 taken with a filter which cuts out these UV & 
violet lines (eg. a minus-violet, yellow, or deep-sky filter), you'll 
notice that the colour is a much purer red - despite the fact that the 
H-beta and OIII lines are still transmitted along with the H-alpha.

My experience, using a high performance Astronomiks UHC filter and E200 
film on the Orion-Monoceros area, is that it records everything in the 
green (H-beta, OIII) and red (H-alpha) channels. Almost nothing is 
recorded in the blue channel. This proves that H-beta and OIII register 
as "green" on E200, not (or hardly at all) as "blue".


Ray "who finds the Astronomiks UHC to be a wonderful filter; fantastic 
visually also in my 120mm f5 RFT achromat" Butler.




Joe & Leslie Schaefer wrote:

> Hi
>   I finished processing my images of the Packman nebula and I was 
> wondering if anyone knows if this nebula has blue in its core area? The 
> image link below is a result of three images (60/90/75 minute 
> exposures). Stacked in PW and processed in PS.  Did I over process this 
> image or is it real?
> Thanks, Joe  
>  
> www.starfillednights.com/image_data/ngc281_image_data.htm 
> <http://www.starfillednights.com/image_data/ngc281_image_data.htm>
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Astro-Photo mailing list
> Astro-Photo@seds.org
> http://seds.org/mailman/listinfo/astro-photo

-- 
Dr. Ray Butler (ray.butler@nuigalway.ie || ray@physics.nuigalway.ie)
Lecturer, Dept. of Physics || Computational Astrophysics Laboratory
National University of Ireland, Galway, University Road, Galway, Ireland.
Tel: +353-91-524411 ext. 3788   FAX: +353-91-525700

_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo