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  #21  
Old 17-05-2007, 11:40 AM
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Originally Posted by [1ponders] View Post
For every 6 degrees rise in temperature the dark current approximately doubles, so 2 degrees is a significant increase. More important than ambient temperature is chip temperature, which can depend on how long the camera has been switched on, whether it has been actively capturing an image a reading it out (more reads / time = hotter chip) etc.
Yeah I see your point Paul, but being cooled I wont have that problem, so really to test them you need them all in the same room at same time - they take a few shots before the test dark. might be hard to achieve, but we could do the canon 400D, 350D, 300D, modded hutech 350D and my cooled beast, and a pentax K10D all at once. Maybe if I talk to Rocketboy might be able to add a 20Da and a 5D to that list. all that photonic energy - might be dangerous - might have to call photonbusters
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  #22  
Old 17-05-2007, 11:52 AM
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Hi all,
OK Houghy for all of us that have yet to get into or contemplate getting into astro-photography how much is a 350D worth and what extra to get it cooled?
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  #23  
Old 17-05-2007, 06:15 PM
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This was taken on a cold night with a 5DH and the seeing was 8+

http://avandonkbl.bigblog.com.au/dat...0509140832.jpg
Zoom in to see detail and lack of noise.
Bert
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  #24  
Old 17-05-2007, 06:20 PM
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Quote:
Originally Posted by avandonk View Post
This was taken on a cold night with a 5DH and the seeing was 8+

http://avandonkbl.bigblog.com.au/dat...0509140832.jpg
Zoom in to see detail and lack of noise.
Bert
Superb Bert !!

Any chance you can post a 1 hour dark frame from your 5DH for the thread?
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  #25  
Old 17-05-2007, 06:39 PM
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amazing stuff! Not so much of a need for a cooled camera at night other than high summer in the far south or tassie i guess? wouldnt hurt tho!
humidity isnt *usually* such a big deal here in SA either it would have too rain a bit more often for that to be a problem.
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  #26  
Old 19-05-2007, 08:44 PM
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I have taken a lot of dark frames at various ISO settings and at room temperature and cooled with the 5DH and with and without INCNR ( in camera noise reduction). This has taken some time and it will take some time to put up a coherent display of images. It has taken all night and day but I have learned a lot. Will post tomorrow. Sorry but good science takes time.

Bert
Here is a teaser a 30 minute exposure at 1600 ISO at about 5 deg C with ICNR.
Here is a 30 sec exposure at 1600 ISO at room (17C) temperature comet Lovejoy should be quite obvious exif data should be intact.
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Last edited by avandonk; 19-05-2007 at 09:14 PM.
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  #27  
Old 19-05-2007, 09:04 PM
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[QUOTE=avandonk;221227]...........................Sorry but good science takes time.

Bert
................QUOTE]

you are quite right, and justly qualified for that statement
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  #28  
Old 21-05-2007, 06:10 PM
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The first thing that strikes you when trying to do an evaluation like this is how fraught it is with your own preconceptions. I have no way of measuring the sensor's temperature directly as the cameras environment does not reflect the camera sensor temperature as the camera's own electronics heat up the camera internally. I first found out that the 5DH would not! do a 60 minute exposure at 1600 ISO!

Where to go from here? Here is a 4min exposure at 1600ISO and processed with ImagesPlus for conversion to Tiff and subsequent digital development at a standard level for all subsequent images. This will give you some idea of signal as opposed to noise.
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  #29  
Old 21-05-2007, 06:30 PM
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Here are two images of dark frames at 1600 ISO and 20 min at 5C and 18C.

Bert
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Last edited by avandonk; 21-05-2007 at 06:57 PM.
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  #30  
Old 21-05-2007, 06:51 PM
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Quote:
Originally Posted by avandonk View Post
Here are two images of dark frames at 1600 ISO and 20 min at 5C and 18C and 20M exposure.

Bert
yes I can see the temperature made a difference but it doesnt explain the amp glow, it is less inthe hotter shot than the cooler one???
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  #31  
Old 21-05-2007, 07:04 PM
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I don't think it is amp glow it is just local heating by ?. Here is why I use ICNR all the time. This is a dark frame twenty minutes at 1600 ISO with ICNR ON. Also I have really pushed the digital development to show these effects exactly the same for all these images.

Bert
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  #32  
Old 21-05-2007, 11:03 PM
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Quote:
Originally Posted by avandonk View Post
I don't think it is amp glow it is just local heating by ?. Here is why I use ICNR all the time. This is a dark frame twenty minutes at 1600 ISO with ICNR ON. Also I have really pushed the digital development to show these effects exactly the same for all these images.

Bert
very impressive Bert.
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  #33  
Old 22-05-2007, 10:23 AM
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Thanks for the comparison Bert, I might give my stock standard 5D a try on darks when I get the chance.
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  #34  
Old 22-05-2007, 11:36 AM
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Here are the settings for digital development in IP.

ImagesPlus Color Project v1.0
Final Image Saved As : H:\000test_5DH\testtwo\CVT_1600_10M _5C.tif
User Comment :
Date: 5/20/2007 17:50
Operation : Read
Apply to: Red Green Blue
Operation : Digital Development
Background : 0
Background Weight : 0.60
Break-Point : 2000
Sharpening Filter :None
Red Emphasis : r
Green Emphasis : g
Blue Emphasis : b

Bert
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  #35  
Old 22-05-2007, 12:07 PM
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Here are some 100% center crops of ten minute darks at 18C. Plus one at 1600ISO at 5C.


200ISO 18C ------------500ISO 18C-------------- 1600ISO 18C------------ 1600ISO 5C
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Click for full-size image (CR_CVT_200_10M_18C.jpg)
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Click for full-size image (CR_CVT_500_10M_18C.jpg)
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Click for full-size image (CR_CVT7_1600_10M_18C.jpg)
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Click for full-size image (CR_CVT6_1600_10M_5C_2.jpg)
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