Dark library (how often to update?)

Alicia Rossiter:
I am interested in getting opinions on how often dark frames needs to be updated?.

About once a year. I recently redid my -10C darks. The purpose of the dark library is to correct for amp glow and compensate for predictable and repeatable pixel response variation.  What darks don't do is reduce noise. So if your lights and flats are being corrected to your satisfaction, there is no need to redo a dark library.

Thanks all, so…it really does not matter if they have been used 6 times or 20 times?. It seems the deterioration is not associated with frequency of use  but rather with how old they are?.  really? If true, them I clearly have to slow down doing this. Thanks again.

Alicia Rossiter:
Thanks all, so...it really does not matter if they have been used 6 times or 20 times?. It seems the deterioration is not associated with frequency of use  but rather with how old they are?.  really? If true, them I clearly have to slow down doing this. Thanks again.

*Doing repeats of a dark library is to compensate for any changes that might be occurring to the camera sensor (or less likely, the electronics) of the camera over time.  For example, while I have not really noticed it, the occasional sensor pixel can go bad.  Maybe becoming a hot (bright) pixel or a dead (black) pixel.  Even something in between.  It is my understanding that these will tend to increase in numbers over time.  I will take a guess that there is also some correlation to the numbers of hours of operation as well.  Others will have much more knowledge about this than I.  In any case the rate of change is pretty slow.  The time that others have mentioned here wait between redoing Dark libraries is probably a safe bet.  My guess is that it can be extended beyond that comfortably and in that, is related to your tolerance of the increase in bad pixels, and other artifacts is acceptable.  Also consider the old libraries as being something that may be worth dating and saving.  As I have been going through my old data, I find that I want to reprocess the stacked images from the subs.  It is best to use Darks from the same "era" as the subs were taken.  Otherwise you increase the chance of actually adding defects to the image.

Libraries are digital data.  There are issues with regard to the integrity of digital data, but that is unrelated to the issues you are referring too in your question.  The handling of digital files by computers has become so faithful, with error checking and correction that it is a non-issue.  In any case, if a digital image file were to degrade, it would likely be "corrupted" and simply would not open.  Your files don't gradually wear out with use.  More likely you should be careful on the media you save your data on too.   And backup data!  But there is not gradual degradation to the files.

Possibly so. 
My one and only astro camera is a ASI 533 MC-Pro that has no amp glow. It’s been about 1 1/2 years since I’ve updated my dark library ( lazy) and frankly, I really don’t see any difference whatsoever using darks or not. 
Since you are noticing amp glow after calibrating with your darks, maybe create a new set and see if that helps. If it does, and it probably will, then you know that you need to recreate your dark library more often.

Jim

Interesting, I have noticed also some banding when the amp glow does not completely disappears. I think I am getting a better understanding on when to redo darks. Also, cameras like ASI183 really create a problem with the huge amp glow. The ASI2600 is the opposite, zero amp glow and hardly any noise.

Do some investigation. Compare dark masters taken 6 months apart. If they only show minor differences then 6 months apart is probably ok. If they show big differences, then you need to shorten the time between dark library updates.

Alicia Rossiter:
I am interested in getting opinions on how often dark frames needs to be updated?. I update my dark library on a regular basis and usually create a new one after 12 uses of any given exposure time/camera. Is this a good practice?. should I do it more often?. I usually stack in PixInsight and get good results but I wander if I am doing this the right way. Thank you in advance for the feedback.

Can I ask a separate question? How many dark frames do you usually include in a library? do you need a separate library for different temperatures, or are you just meaning for use with a cooled chip (like all photos at -10 C)?

I personally shoot for 15-20 darks at whatever temp I decide to work with. If you shoot with different temperatures through the year yes you should take darks at the same temp you shoot your light frames at.
In my case I shoot year round at -5

Dale