Hi Tyler, Thanks for your interest. On 29 Mar 2010, at 09:35, Tyler Allred wrote:
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.
The center is blown even in the 30" shots so I was not surprised when the 60" and 120" shots were also blown.
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 don't have room to post all of the images at once so let's start with the raw 120" exposures since there are only 10 of those. There are 20 60" and 40 30". I've posted all 10 of those along with the 120" master dark (made from 15 120" darks) and the master flat (made from 25 flats, each of which I first subtracted a master dark from): http://users.wirelessbeehive.com/~paw/temp/M81-02.ZIP Light, dark and flat were all shot at -10 and the camera binned 2x2.
I have a few questions: Are you adding the frames when you combine? Averaging? Sigma? What type of combine are you using?
The software gives me a choice of Add, Average and Median Combine. For the darks and flats I used Median. For the light images I used Add. I don't know what "sigma" is.
I suspect you might be adding and exceeding the range of a 16-bit image.
Another thing I don't understand. :( I look forward to seeing what you come up with. Good luck, patrick