From: Milton Aupperle <milton@outcastsoft.com>
Date: October 31, 2007 10:08:54 AM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: [Astro_IIDC] Comet Holmes Oct 30 from Toronto
Hi Jim;
On 31-Oct-07, at 8:48 AM, jimchung2338 wrote:
I thought I'd experiment with longer exposure imaging with the PGR Flea using that most
convenient of recent target - Comet Holmes. Subs were taken at 5s with automatic dark
frame subtraction via AstroIIDC.
http://tech.groups.yahoo.com/group/Astro_IIDC/files/Planetary/Holmes_FleaRGB.jpg
I think the colors are faithful and there is siginificantly less green in the outer cloud as
compared to a shot I took 2 days earlier with my Starlight Express CCD.
Nice Shot. I have yet to see it and my viewing area has been severely restricted. As of last week because of a 15 story sky crane went up a block to the south of me. The boom is long enough that it can almost extends over top of my domicile.
Milton, are you planning to change the algorithm used in sum stacking images. Using
AstroIIDC I can really only stack about 10-12 5s subs before I reach the maximum white
levels values in the comet nucleus. I had to resort to exporting the movies as individual
TIFFs and stacking them in another program. There wasa real benefit in stacking the full 5
minute exposures in terms of noise reduction.
I'm not sure what we are supposed to do differently. Summing one frame to the next frame is just that, adding them together. It's the same algorithm as the normal stacking, it just doesn't do the divide with the number of frames to calculate the average.
So what method were they using in this "other program"? Log Stack, under weighting each frame by a given amount, median combine or what exactly?
HTH..
Milton J. Aupperle
President
ASC - Aupperle Services and Contracting
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