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Old 13-01-2012, 03:05 PM
mork (Pieter)
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Line in new ATIK 383l

Hi,

My brother took delivery of his new camera today, fired it up and we can see a line in the image.

The line is there in every shot, even at -5C and with the shutter closed.

Is this normal and something for dark subtracts to remove or should we return it as faulty?

Thanks,
Pieter
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Old 14-01-2012, 04:26 PM
mork (Pieter)
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Was advised by an IIS member that "the KAF8300 chip is not supposed to have any column defects" so am now in touch with Atik who asked for samples.


0.001 sec uncooled http://dl.dropbox.com/u/30656039/Tests_001.fit
0.001 sec cooled http://dl.dropbox.com/u/30656039/Tes...ed-10c_001.fit

10 sec uncooled http://dl.dropbox.com/u/30656039/Tests_010.fit
10 sec cooled http://dl.dropbox.com/u/30656039/Tes...ed-10c_010.fit

Regards,
Pieter
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Old 15-01-2012, 07:52 AM
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The specs are stated with 1.5% threshold. So i think that it needs to be over this before it is regarded as a defect.
You need to see how many pixels are affected, over the total number of pixels on the CCD. If its over 1.5% then you may have a case.
Though if its under 1.5%, it may well be within limits.

Have a read here : http://www.cloudynights.com/ubbthrea...8/Main/4973764

Theo
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Old 15-01-2012, 08:28 AM
mork (Pieter)
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Thanks Theo,

The link is very useful.

One interesting comment there was "Quite often people mistake a hot pixel readout as a column defect. That will appear as a bright line that goes from the bottom of the frame to a point short of the top. That will be removed with a proper calibration." That fits with what we are seeing.

Waiting on a clear night so we can capture some real shots.

Regards,
Pieter
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Old 16-01-2012, 08:58 AM
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Yes,normal for the grade chips they use in the 8300's.

The ST8300M has them and of cause these are removed with dark's,and also FLI ML 8300 has them but,If the cooling is sufficient enough like in the FLI's these defects magically disappear.
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Old 17-01-2012, 05:32 PM
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My FLI ML8300 developed one that disappears around -5C and I usually operate it at either -35 or -40C where it is absolutely perfect.
You are right - its hot pixels that get dragged along in the readout process. When I bought it it did not have any. I guess it appeared about 2.5 years later. Perhaps earlier as I don't normally view the chip until its chilled and it does not show then.

KAF16803 chips often have a couple. Mine had none and developed one after 1.5 years. CCD chips also age from radiation damage and could develop a line like this at any time.

Then it becomes a matter of how many is acceptable? Ideally you would have none but that is not the real world of CCD chips.

If you make sure your darks are fairly recent or updated especially if one appears it should dark subtract out if you combine enough darks and make sure they are at the same temperature.

Greg.
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Old 17-01-2012, 05:47 PM
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Dither during imaging , it will disappear on alignment and stacking.
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Old 23-01-2012, 06:04 PM
mork (Pieter)
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Just writing to update those who might be interested. The weather has been difficult (that seems to be a pattern whenever you buy new equipment) limiting the number of shots. Another disappointing thing is that ATIK have not got back to us.

Chilling to below -10C makes the line mostly disappear. Stacking fixes it up nicely.


Thanks to all who helped work this out.
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Old 24-01-2012, 09:43 AM
mork (Pieter)
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http://www.dropbox.com/gallery/25160...amera?h=12f9b0 for several differently processed images of M42.

They were processed from the same files, some 30s, many 60s, and some 300s exposures. Guiding was lost at one point.

Meade LX800 10" scope on a Celestron CG5 mount (which is not really up to the job)

Regards,
Pieter
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