Strange patterns with 383L+ CCD

Marcel

Member
I found this strange pattern in my recent images. Like strings that run in a right-upward direction.
I see them in my stacked uncalibrated frames as well as in my calibrated frames.
The pattern is also pronounced in the high rejection map.

See attached pictures of the stacked frames.
This is 45x600 sec stack of S2 frames. Same pattern but less in O2 and Ha.

Camera (Atik 383L+ CCD) was cooled to -15 with an ambient T of abt. 20c

My suspicion is that this has to do with ambient T as I have seen it before in summer but not in winter.
Has anybody seen this before? Any suggestions of an explanation?

Thanks in advance for any help.

Marcel
 

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Frosting on the sensor chip. A delta of 35 is a big ask for the 383 so the Peltier will be running full bore. Recharge the drying tablets, leave in for 24 hours and then recharge again. Repeated frosting can leave a water mark on the chip so worth doing soonest.
 
Thanks Chris for your suggestion.
My drying tablets definitely needed recharging.

What solved the problem in the end was my dithering settings.
I was using the default value of 2 pixels; way too low.
Changing it to 20 pixels solved the problem.
I now have clear frames w/o artefacts.

M
 
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