M101 from France

[MarkS]

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.

[Fay]

You have done really well Mark. Never thought an unmodified 300D could go that far. Dark skies are a rare thing

[Mike]

Nice image Mark. I'd hate to think what you would be producing if you had a cooled CCD !

[RobertM]

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...

[MarkS]

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  But the flats are a bit out of date - there are a few dust bunnies in the image - I need to shoot some fresh flats and reprocess it.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.

[RobertM]

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.

[JohnP]

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

[MarkS]

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):



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.

[RobertM]

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 !