Re: [APML] Cygnus on E100S

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

Dave,

As a widefield fan, I love everything I've seen produced by these Borg 
f4 systems - especially by you and by Jon Kolb. You have really brought 
it to the max with that 4x5 inch camera.

My advice on the nicest presentation would be:
1) Flatfield-correct the vignetting where it is moderate (down to say 
50% illumination). This will maximise the FOV impact.
2) Establish the centre & radius of the vignetting falloff, and do a 
hard circular crop of everything beyond the radius where the image 
flatfielding ceases to be acceptable
3) Do a rectangular crop on what's left to make the circle symmetric 
from left-right (and optionally from top-bottom).

This will give you a nice flat image containing as much FOV as possible, 
with a sharp-edged framing & aestherically symmetric rounded corners.

Ray "who does this with 6x4.5cm shots vignetted through a 2-inch 
focuser" Butler


D. Kodama wrote:

>Hello,
>
>I've been trying to dial in my large format shots with E100S.  This is a
>full-frame 4x5 test from last weekend:
>
>  http://www.eanet.com/kodama/astro/2005/0813/index.htm
>
>I will probably try exposing longer next time, but I was very pleased with
>the color balance at this exposure (30 minutes).  I did no color
>adjustment at all.  The only photoshop processing was a curve adjustment. 
>Too bad E100S is obsolete.  :(
>
>Given the vignetting, I'm interested to hear if you prefer to see:
>
>  - the whole frame
>  - rectangular crop to unvignetted area
>  - circular (oval) hard frame
>
>Thanks,
>
>Dave Kodama
>
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-- 
Dr. Ray Butler
Lecturer, Physics Department & Computational Astrophysics Laboratory,
National University of Ireland - Galway, 
University Road, Galway, Ireland. 
Web: www.nuigalway.ie/physics/ 	Email: ray.butler-AT-nuigalway.ie 
Tel: +353-91-493788 		FAX: +353-91-494584

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