Re: [APML] M51 RGB (only)

["John Boudreau" <jeboud@attbi.com>]

Great job Tony, and thanks for your processing details.

One minor thing that I notice is that for an image that was merged into an
RGB in RegiStar, that the color channels look slightly misaligned. It's most
noticable looking at the red/orange stars in the upper half of the image.
Any idea why?

John Boudreau
jeboud@attbi.com
http://home.attbi.com/~jeboud/astro.htm

----- Original Message -----
From: Tony Hallas
To: astro-photo@seds.org
Sent: Sunday, April 21, 2002 2:38 PM
Subject: Re: [APML] M51 RGB (only)


Howdie folks,

    So.... following Rob's lead, here goes: I have been putzing around with
color information via a CCD instead of film... guess what? Noise is still
enemy #1. So the same rules apply here that apply to film... shoot lots of
images and average. I gathered up all the bits and pieces that I had on M-51
and did all the "reduction" process on them... this is the same as cleaning
up photo images by getting rid of vignetting, dust spots, etc etc etc.
    Then these files, all in 16 bit info, were imported into Registar to
average and merge into a 16 bit RGB. By combining the RGB before any curves
or post processing was done, the color balance as dictated by the filters
and exposure times should be pretty much "locked in."
     Then I took the file into PS and gently applied curves and some level
corrections for the black end point to compress the data. I applied a slight
amount of saturation to the image. Basically that's it. What I got, I think,
is a pretty close approximation of the true colors of M-51 since this is
"pure" RGB... no L, no nothing. Note that the little galaxy at the bottom is
very blue... active star formation or something, and there is an interesting
blue arm from the main galaxy near the companion... in color you can see
from this that M-51 is probably in front of the companion which is a
different color... in the 200" image you can see this as a string of
material from the main galaxy but it is in B&W.

     http://www.astrophoto.com/M51RGB.htm

     Tony


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