RE: [APML] Witchhead Challenge

["Scott Hammonds" <shammonds@creatorsview.com>]

Juan, Brian, Alan,
Thanks for posting. This sort of thing is always interesting to me to see
the different results using the same data. All very nice job for what data
you had to work with. Alan, you should post, that's the way to learn. Juan,
really nice job bringing out the details.  



Scott Hammonds
www.creatorsview.com



-----Original Message-----
From: Juan Conejero [mailto:pleiades2004@pleiades-astrophoto.com] 
Sent: Friday, December 10, 2004 10:03 AM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Witchhead Challenge

Hi Scott,

This is my version:
http://pleiades-astrophoto.com/tmp/APML/witch_challenge_pi.jpg

Processing includes: background modelization and subtraction (vignetting
correction), histogram transforms, separate curves transforms to the
combined RGB channel and luminance/saturation, noise reduction with SGBNR
and wavelets, saturation adjustments, and a star shaping procedure.

I must say that noise reduction has been extremely difficult for this one. 
You have put all of my noise reduction resources to their limit!

I had to apply very drastic curves to unveil extremely faint nebulae. As a
result, stellar disks grew in diameter too much. Stars were way too
prominent at the end of my processing, so I decided trying a star shaping
procedure. I extracted the luminance to build a star mask, and applied an
erosion (minimum) filter through it (Mike Cook's method, masked). The mask
includes almost every stellar object in the image. This has been possible
with wavelets. I used this mask also to enhance the color saturation of
stars.

Finally, I extracted the green channel from your original image to build a
second star mask. Through this mask I applied a slight sharpening process
with wavelets to recover the original stellar resolution. The problem was
that most small stars in the image had lost their peakwise profile, and the
overall aspect was too "plain". The masked sharpening process fixed this.

Hope you like it. Thank you for putting such a difficult challenge :-)

Juan
________________________________________________________________________

Juan Conejero, Pleiades Astrophoto Team
PixInsight Home Page: http://pleiades-astrophoto.com/pixinsight/
________________________________________________________________________

----- Original Message -----
From: "Scott Hammonds" <shammonds@creatorsview.com>
To: "'Discussion of Film Astrophotography'" <astro-photo@seds.org>
Sent: Thursday, December 09, 2004 7:24 PM
Subject: [APML] Witchhead Challenge


> Ok, as promised, here is the processing challenge. There is a slight bit 
> of
> elongation of the stars in some areas, possibly from film creep or 
> flexure.
> It's not too bad.
> This file is 9mb. It is a stack of 2 60 minute exposures on hypered RG200
> Select film, combined in Registar.
> It was originally scanned at 4000dpi and has been cropped and resized at
> 2000dpi to facilitate faster download.
> Good luck, I look forward to seeing the posts here on APML.
>
> http://www.creatorsview.com/astrophoto/untitled.html
>
> Thanks,
> Scott Hammonds
> www.creatorsview.com 


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