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Old 16-02-2013, 08:57 AM
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Grimmeister (Anthony)
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Central DS camera Darks

Hi Everyone,

A little while ago the question was asked about how dark the Central DS1100 Darks really were? JJJ did a comparison of her 550D to the CDS-100D camera here is the thread: http://www.iceinspace.com.au/forum/s...d.php?t=102944

I thought I would do a more direct comparison as I have just taken receipt of my Central DS CDS-600D and I also have a standard non modified in any way EOS 600D Camera. so I am comparing apples directly to the same apples.

I have done two tests: one at ISO 1600 and the other at ISO 400 both for 10 minutes, the Central DS Camera had the cooler running naturally and the Standard 600D Camera was just that! running standard, the ambient temperature was the same for both tests as I had the Air Con running at 23'C so the house could be considered a constant.

I have taken the images and blown them up to 200% and taken a copy and pasted them side by side for comparison and labelled accordingly.

One thing not so obvious is the temp increase on the standard camera, I did the ISO1600 and then straight away the ISO 400 tests on a camera so the ISO 400 shot was after the camera had been running for 10 minutes already, the temp sensor in the Central DS Camera added only 1'C after 20 minutes continuous exposing, the EOS 600D added 7'C after the 20 minutes exposure time.

Anyway I think the images attached speak for themselves, I was very please to see the difference and cannot wait to get the camera under the sky and take some images.

Cheers

Anthony
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Last edited by Grimmeister; 16-02-2013 at 09:14 AM.
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Old 16-02-2013, 09:50 AM
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wasyoungonce (Brendan)
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Jeez that looks good.. Just one thing on darks...do you use an alloy cover on the camera for darks? Some IR energy can pass thru plastic covers and be detected by the sensor.
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Old 16-02-2013, 11:11 AM
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Grimmeister (Anthony)
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Hi Brendan,

No I used the plastic canon covers as I didn't realize these would leech IR into the sensor

However during the test above both darks were taken with the same plastic cover and in the same location so I would expect any variance due to this to be minimal.

Will definitely keep this in mind for my darks that I use for images.

Cheers

Anthony
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Old 16-02-2013, 11:27 AM
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wasyoungonce (Brendan)
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Yep I thought you would use the plastic dust cap on both ...this not a great issue just a small trap.
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Old 16-02-2013, 05:21 PM
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jjjnettie (Jeanette)
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I've not used darks with any of the images I've taken with my camera, yet.
Multiple subs seem to clean up what little noise there is quite nicely.
Great comparison too. Such a difference.
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Old 16-02-2013, 08:43 PM
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To get a really good indication you can use noise measuring functions in programs like Nebulosity or CCD Stack. To get a correct representation, compare a bias frame to a dark frame.
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Old 18-02-2013, 04:16 PM
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philiphart (Phil Hart)
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Nice test Anthony.. thanks for posting it. I'm still a very happy owner of my CentralDS Astro40D and having been using it on Comet Lemmon over the weekend.. in 30 degrees ambient I'll take any cooling I can get!

One thing that would be interesting to test as well is how a single dark frame looks after subtraction of an average dark frame. ie.. to what extent are those hot pixels repeatable (and can therefore be subtracted out) and how much is actually random noise?

Phil
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Old 18-02-2013, 05:28 PM
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Hi Phil,

I will see if I can do a test later this evening and post the results, from my experience with my standard EOS 600D I would say yes the majority of noise would be reproducible each time and can be extracted with an average dark frame.

Cheers

Anthony
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