Hi Tyler, On 24 Mar 2010, at 22:53, Tyler Allred wrote:
I always apply calibration frames first... then align and stack... then stretch.
Good to hear. I was afraid I was going to have to stretch each image. I just went back and applied the master dark and master flat to each image. No need to align as all five images were guided. Added them all together and did a bit of stretching. Nothing pretty but it does show there's a lot of data lurking in even 2.5 minutes total exposure time. Course to show all that I had to really blow out the center: http://users.wirelessbeehive.com/~paw/temp/M81-02.JPG As compared to the unstretched version from yesterday: http://users.wirelessbeehive.com/~paw/temp/M81-01.JPG And for those who might want to play around with the original stacked FIT image, here it is: http://users.wirelessbeehive.com/~paw/temp/M81-01.FIT
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. Ought to be fun and it'll give me data to play with on cloudy nights. And like before I'll make them available to anyone else wanting to play with them.
That is generally true as long as you are not saturating too many stars in the image or other areas of interest.
Checking the 30" shots I found at least one star that was already saturated so I'm guessing it'll probably bloom in the longer exposures. Happily it's on the edge of the field and will be easy to crop out. Interestingly the burnt out core of the galaxy was not even near saturating. One other challenge is the corrector plate. I've not cleaned it since last spring and it shows. Guess I'll bring the OTA inside and pull the corrector and give it a good washing (now let's see, where did I put the Brillo pads... <g>). Thanks again Tyler. And I was serious about hoping you might make it to SPOC one evening and shoot and process a few images there. patrick