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Possible problem with APT, existing dark library and ZWO cameras


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I just finished a cheeky imaging session on the california nebula. Subs looked good.

When I processed them I used dark frames from my usual dark library - 240 secs, unity gain, -10C.

DSS spat out an image that was very blue.  When I took it to photoshop and converted it to 16 bit... what a shocker.

The image was white with black stars and very pixillated nebulosity.  It was almost as if the red channel had been lost.The histogram was fully shifted to the right.

Playing in DSS I stacked lights on their own - all okay. Then lights + flats - all okay.  As soon as I added darks the problem came back.

(I have to check Bias files)

The only change to my system was an upgrade to Astrophotography Tool 3.87 on Sunday.  My dark library was created on an older version (3.85), and until last week had been working fine. I know there's a change in the new version to provide better support for ZWO and Altair Cameras. I wonder if this has affected old dark files.  It doesn't make much sense why that would be the case... I'm kind of thinking some kind of debayering thing (purely guessing)

I tried stacking with some 300 second darks I created on 3.87 yesterday and it worked as expected (the result was horrible, but predictabe - all data was present, albeit looking bad due to the incorrect darks)

I have no idea if this is a normal occurance with APT updates.

It's late now, but I will recreate some correctly calibrated darks and re-stack tomorrow.  

Anyone else experienced this? It seems to be a very odd occurance. (it could be my inexperience or maybe I missed something)


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Nothing worse than a stale flat!

DSS was nagging for an update, but I have not done it yet. Another reason I suspect it's APT at the heart of it is that in 3.87 the preview images have a green tint when auto-stretched (previously I found them more blue).

Best thing is it was an easy fix and I'm glad I had accidently flicked on a setting in DSS

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