Re: [APML]: Image registration [Was: Latest Tony Hallas Images]

[Axel Mellinger <axm2@canopus.physik.uni-potsdam.de>]

The Astro-Photography Mailing List
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On Fri, 11 Sep 1998, Eric Royer wrote:
> 
> Why did you use the galactic coordinates instead of the RA and Dec ?Was that just
> easier as you wanted to have the long axis of the final image parallel to the
> galactic plane ? or is it really important to register the images correctly ?
> I think that you can change from galactic coordinates to RA and Dec with a
> translation and a rotation.
> 
Any coordinate system is fine, but for a Milky Way panorama the galactic
system was the obvious choice. If fact, I input the RA and Dec coordinates
of the reference stars which are then internally converted to  galactic
longitude and latitude.

As for the accuracy, I got the rms error down to 0.5 pixels on a 1500x1000
image. I did have to use a 3rd order polynomial fit, though, to accomodate
a slight distortion causes by the lens. More about that in my upcoming
article on my web page. Processing time is about 3-5 minutes.

Clear skies,

Axel

-- 
Axel Mellinger  <http://canopus.physik.uni-potsdam.de/~axm/astrophot.html>