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PostPosted: Thu Oct 01, 2009 12:29 pm 
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Hi folks,

I've yet to try my 5D MkII out as a tool for astrophotography largely because I've been without a notebook PC for the last year. But my attention was drawn to this article on the excellent Christian Buil site (software and hardware) comparing the Canon 40D, 50D, 5D, 5D Mark II cameras and, incidentally, a dedicated CCD chip, the Kodak KAF-3200ME. The Kodak chip wins hands down (no surprise there) but obviously that's very specialised kit compared to the general purpose DSLRs.

But a couple of images drew my attention as they illustrate how badly Live View can affect sensor performance when you are struggling to make best use of every photon.
    Image...............................................Image
    Part of a RAW image taken in the dark with the 5D Mark II just after power on.
    ................The same part after 10 minutes of LiveView display.

    ..............The exposure time is 300 seconds for the two situations. The dark signal increase by a factor 5 after a long LiveView session.
I think the moral here is to wait as long as you can after using Live View as a focussing aid before starting a sequence of exposures. My own previous experience with a 40D taught me that it also pays to give the sensor a chance to cool down between exposures. Pretty obvious stuff, I suppose, but it's easily forgotten in the heat of the moment, especially when you see those clouds oiling in. :evil:

Bob.

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OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Thu Oct 01, 2009 5:42 pm 
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Hmm... I tend to shoot continuously so I'd guess that would have a similar effect to using live view a lot? Something to look out for.

On similar lines, I find on the Sony A350 after a long shooting session, a long exposure I get purple glow creeping in on the top two corners which isn't there when I start.

I can only hope for the weather to get colder faster to help offset this :D

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PostPosted: Thu Oct 01, 2009 6:41 pm 
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This is one of the main reason TEC Cooled CCD as so popular in astrophotography. I bet it is possible to build a cooled regulated enclosure for your DSL camera but you have to be aware of the weight you will be added to your mount.

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PostPosted: Thu Oct 01, 2009 7:09 pm 
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Symtex wrote:
This is one of the main reason TEC Cooled CCD as so popular in astrophotography. I bet it is possible to build a cooled regulated enclosure for your DSL camera but you have to be aware of the weight you will be added to your mount.

It's been done. I imagine there are others out there but the only company I have bookmarked is this one:
    Image
Bob.

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OM-D E-M1 + ED 12-40mm f/2.8, H-F007014E, M.ZUIKO DIGITAL 45mm 1:1.8, M.ZUIKO DIGITAL ED 75mm 1:1.8, L-RS014150E.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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