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RE: [APML] First images posted: vignetting correction,circular cropping
Hi Ray!
> [...]I have concentrated on squeezing
> the most out of them
> by developing my own digital processing methods.
Sounds that we'll have a lot to talk about ;-)
BTW, do you know C++?
> The
> problem with this
> is that it can go on forever - one is never entirely
> satisfied with the
> result. Little gotchas always remain, especially the
> higher order
> residuals when one tries to do photographic
> vignetting correction..
Are you using a polynomial radial fit to the data? I
think that Wei-Hao used to do so up to the 7th order.
I have been working with a two variable polynomial
(Cnm*x^n*y^m,n+m<=N) and had some problems with N>6 (I
guess that it is workflow). Anyway, this far a spline
interpolation sounds to be the best way to go.
Another good point is how you remove the vignetting.
Just substraction?
> - Automated multi-scan scaling & coaddition with
> scanner saturation
> removed by masking
Could you explain this a little further? I don't
understand what you made here.
> - Automated rebate intensity subtraction and rebate
> cropping
The same :-P
> - Automated channel registration (lateral colour
> correction)
How do you register the images? Fourier correlation?
Is it just a scaling factor?
> - Automated vignetting/gradient correction (could be
> a bit better)
Do you put some sample boxes, or just play with the
statistics of raws and columns?
> - Automated circular cropping (- Dave, this is what
> you wanted to see)
Anything special in that automatization? Do you
manually put the radius of the circle?
> - Automated levels set by image's own statistics,
> for final RGB
> recombination
Have you seen my AutoH software?
http://pteam.pleiades-astrophoto.com/carlos
(BTW, I have finished a pair more programs... I need
to correct the documentation to upload them propperly)
>
> I guess this is the point where I am supposed to
> say: "Comments &
> criticisms welcome" !
I just have to say that I am very interested in the
astronomical image processing field (as researcher).
I'm finishing my pregrade astronomy studies and want
to work later in that field. I would be very glad to
discuss with you all of this (your techniques) =)
I know that all of this has little to do with
professional works, but, who knows? there could be a
connection somewhere.
Regards,
Carlos Milovic F.
-------------------------
Astro & Photo - CMF
http://www.astrophoto.vze.com
-------------------------
Visita "AstroFoto", el foro de astrofotografía en español
http://espanol.groups.yahoo.com/group/astrofoto
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