M101 (Pinwheel Galaxy) from my weekend in France
Canon EOS 300D on the Celestron C11 + EQ6 mount
Guided using a 300mm telephoto lens with SPC900 webcam stuffed in the back.
24 x 5min subs.
The stacked image image was 2x2 binned then cropped.
(http://homepage.ntlworld.com/the_shelleys/Astronomy/m101_020508.jpg)
You have done really well Mark. Never thought an unmodified 300D could go that far. Dark skies are a rare thing
Nice image Mark. I'd hate to think what you would be producing if you had a cooled CCD !
That's pretty impressive Mark as it's a very low surface brightness. Did you take calibration frames i.e. flat fields, darks (not sure whether bias apply) I assume that you bin in Iris ?
That reminds me I need to finish off my M101...
Robert, I always use darks, flats and bias frames. It's essential for getting good results with my Canon. But the flats are a bit out of date - there are a few dust bunnies in the image - I need to shoot some fresh flats and reprocess it. I use Iris for all my processing (though I often use DeepSkyStacker to give me a quick preview!)
I'm interested to see just how far I can push the unmodified Canon. Dark skies certainly help tremendously.
However I am beginning to become frustrated at the lack of Hydrogen alpha sensitivity so I may end up doing a DIY modification at some point.
Given a dark sky there's obviously a lot you can do with a DSLR even in unmodded form but noise is still your worst enemy. It'll be interesting to see what results you get when the weather warms up.
Mark - pretty darned impressive for an unmodded dslr on a really difficult object. Looks like stars are slightly elongated - were you having guiding issues or is it something else?
John
John,
Yes, I had a guiding issue - there were no bright stars in the vicinity for my unmodded webcam so I had to use a 4sec integration time to get the signal to noise ratio high enough for PhD to guide.
Robert,
You're right about the Summer. As a laugh on Sunday afternoon, I took a dark in the shade (ambient temperature around 25C). 10 minutes at ISO 800. This is the result (exactly as it came from the camera - no stretching applied):
(http://homepage.ntlworld.com/the_shelleys/photos/CanonDark25C.jpg)
From it I've calculated the dark current to be just over 1 electron/sec/pixel at 25C which accords well with other figures I've seen on the Net.
Not sure how much truth there is in it but I've read that the CMOS sensors heat up over the course of a long exposure so need a little time to cool off between shots, especially when the ambient is high. It might be worth checking.
Looks like a cooled DSLR is the way forward and with the price of second hand 350's coming right down it'll only be a matter of time before someone posts details or a kit. Cooled colour 6MPix camera for a few hundred quid - who could resist !