Patrick, These images are very interesting. The stacked frames look good, however, I don't think the center should be blown out on any of these images. Also, the 1 hour image is more blown out than the others, which should not happen. Can you send me the raw fits files (not calibrated), or provide a link to a zip file etc.? I would like to take a run at processing them to preserve the central portion of the galaxy. I am certain that your software is stretching and clipping in your process somewhere, without you knowing it. I have a few questions: Are you adding the frames when you combine? Averaging? Sigma? What type of combine are you using? I suspect you might be adding and exceeding the range of a 16-bit image. Cheers, Tyler -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Patrick Wiggins Sent: Sunday, March 28, 2010 4:27 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] M-81 On 25 Mar 2010, at 03:25, Patrick Wiggins wrote:
Hi Tyler,
On 24 Mar 2010, at 22:53, Tyler Allred wrote:
My guess is that you will do better with fewer frames of longer duration.
And to that end I took advantage of tonight's cloudy skies and shot a whole slew of 60" and 120" darks which I made into master 60" and 120" darks. Next clear night I'll do a bit of experimenting and shoot 10 120", 20 60" and 40 30" guided shots of M-82 and see which set nets the best image. Hey, and then I can stack them all together for a total of 1 hour exposure time.
Though the sky was a bit hazy and very mooney tonight I ran the test. The results are in a ZIP file located here: http://users.wirelessbeehive.com/~paw/temp/M81.ZIP The file contains 4 FITS files, one a compilation of 40 30" exposures, one 20 60", one 10 120" and one is a compilation of everything (1 hour total time). The posted files are what I got when I reduced the raw images with flats and darks (I even first applied darks to the flats) and then stacked them. Aligning was not needed as I guided the whole hour. However, I did not do any stretching so as to give anyone interested a chance to play with the images. I can also supply all of the original files if anyone wants to experiment/practice with those. patrick _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com