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Old 13-10-2020, 02:56 PM
MarkInSpace (Mark)
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I dont need to collect dark slides every time... do I?

I am using an ASI294MC Pro. If I standardise my subs at 120 seconds at -5Degrees, do i need to collect dark frames every time, or is once enough?
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Old 13-10-2020, 03:24 PM
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Merlin66 (Ken)
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Mark,


https://astronomy-imaging-camera.com...94mc-pro-color


The dark current is so low <0 deg I'd say you're pretty safe with reusing a master dark.
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Old 13-10-2020, 05:06 PM
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Nikolas (Nik)
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No that's what a dark library is, so long as you shoot lights with those settings. If you change settings on your camera then do the same with your darks, they are then part of the darks library.
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Old 14-10-2020, 01:44 PM
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i just got got a new camera and that is the first thing I do. Lock it in a darkened room and run through a sequence of all the typical exposure lengths, gains etc I plan to use and store in separate folders good to go. Should be good for some considerable time
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Old 14-10-2020, 01:48 PM
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I redo darks for my asi071 every 6 months. Why? Answer = dunno, but you don't need to do it every session.

I'm paranoid about flats, so do them every session.
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Old 14-10-2020, 03:50 PM
glend (Glen)
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Dark libraries are a common tool imagers use, just as long as you have sets that match sub exposure duration and temperature setting. Bias is the same. Some cameras can actually get away without Darks, like the ASI1600MM-C, IF you are shooting subs of short duration (say 30 secs, up to 60 sec) where there is no detectable AMP glow, just use Bias in that case. It is up to you, look at the Bias and Dark histograms and see what you think.
Of course the ASI294 is a different sensor, and has different needs, and issues. From my research it seems to require Flats as well, given the uneven sensor cooling producing gradients (a product of the back lit architecture not allowing a full sized TEC).
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Old 14-10-2020, 04:11 PM
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Darks? What are those? (I use Starlight Xpress CCD's)

With my SBIG's, yes, I keep a dark library.
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Old 15-10-2020, 07:18 AM
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Darks can work for a long time. CCDs generally slowly degrade over time so they may develop columns and extra bad pixels.

CMOS will too but at what rate I don't know but these same CMOS sensors in mirrorless cams redo the bad pixel map once a month. So the fact your digital camera may be clean is because it does this routinely.

I also don't see any CMOS camera suffering from those hot columns that a lot of the KAF series CCD sensors do. But I have used 3 year old darks very occassionally and they worked nicely.

But with CMOS you need multiple darks to match the various settings as that all needs to be exactly the same as your lights.

So I would:

1. Standardise a temperature that can be achieved all year round and the lowest you can reliably achieve.
2. Use only 2 settings for gain, one for regular imaging and one for narrowband.
3. If you are using QHY that would be the readout mode for each type of imaging.

The usual advice for CMOS (not sure about the 16bit sensors) is not to use bias frames and use flat darks when making flats.

Greg.
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