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M33
Nov 13, 2009 12:32:13 GMT
Post by martin180 on Nov 13, 2009 12:32:13 GMT
Hi All, With clear skies from dusk on Tuesday to 4am on Wednesday, I decided to spend the entire astro session imaging M33. David Stewart had posted an image of M33 taken with a ccd camera and I wanted to compare in so far that I could, with dslr cameras. I also wanted to image the galaxy,a difficult low light target and I also wanted to capture the magnificant HII regions within the spiral arms of M33. I initially imaged with a Canon 5D MkII and over three hours secured 90 subframes with iso values of 800 and 1600.I then imaged the galaxy with a Canon 50D modified for one and a half hours again employing 2 minute sub frames and using iso values of 800 and 1600.The attached image is from the latter camera. A hurried processing from the 5D produced a disappointing result. I will re process and submit the result to the forum in due course. Clear skies and a big thank you to David for providing the inspiration. Martin Attachments:
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M33
Nov 13, 2009 13:05:46 GMT
Post by brianb on Nov 13, 2009 13:05:46 GMT
A good result!
Could I suggest you try turning down the ISO to 200 or 400. If you're using an astronomical stacking program you don't lose any light grasp but you do get an increase in dynamic range; winding up the ISO makes the brightest points "clip" sooner. The image on the preview screen does look darker (maybe even completely blank) but the faint objects are still there & a stacking program like DSS or AIP4Win will display them just as well.
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M33
Nov 13, 2009 23:45:00 GMT
Post by bigeye155 on Nov 13, 2009 23:45:00 GMT
Martin,
Lovely shot of M33, the Ha regions stand out really well too. Your modded 50D is the best camera for astro work, with its extended overall response especially into Ha. There is no benefit in using the 5DmkII as its not modified, and you don't need the extra pixels anyway. The benefit of extra field of view in the 5DmkII is offset by the need to have an excellent optical system with a flat field, which you have in your Epsilon, but the APS chip with that scope gives a large field suitable for a lot of targets. 800 ISO is reckoned to be the upper limit for DSLR imaging before a loss of DR. Can you increase your subs to 3 or 4 mins before trailing or sky fog kick in?
David.
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