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Stacking images from different sessions

Astrophotography
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#1 Dmitriy365

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Posted 28 November 2021 - 01:16 PM

Hello,

 

There may be a thread on this but I could not find it.

 

I would like to stack images from multiple nights. My concern is not necessarily the images themselves but the calibration frames. Obviously each session can introduce its own noise/dust etc. Do people just average these out and make one master calibration dark/flat etc, or is there a better way to address this in DSS and remove noise from each session before stacking it all together?



#2 Corbemar

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Posted 28 November 2021 - 01:27 PM

Hi,

in DSS you can stack data from multiple sessions putting them in different groups. You can see the groups as labels on the bottom of the file list.

In each group you can put the lights of a session and the related calibration frames.

DSS will first correct the light frames applying the calibration of the same group, before calculating the final stack of all calibrated lights.


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#3 gerryberry

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Posted 28 November 2021 - 01:35 PM

Did this for the first time recently and collected flats and darks for each night, calibrated each night separately then altogether using pixinsight. The advice I got was always take calibration frames even if imaging same thing different nights
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#4 Dmitriy365

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Posted 28 November 2021 - 07:38 PM

Hi,

in DSS you can stack data from multiple sessions putting them in different groups. You can see the groups as labels on the bottom of the file list.

In each group you can put the lights of a session and the related calibration frames.

DSS will first correct the light frames applying the calibration of the same group, before calculating the final stack of all calibrated lights.

Thank you! Knowing that DSS can do that is awesome. Once DSS makes the master frame, do you delete the individual subs to save disc space? Not the lights obviously. 



#5 OldManSky

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Posted 29 November 2021 - 08:29 AM

You can re-use dark frames over and over again, there's no need to re-do them every night as long as the sensor temperature of the lights (and darks!) is the same.

Most of us create dark libraries (for specific temperatures, gains, exposure times) and use them for many months.

 

You can re-use flat frames IF you haven't moved the optical train (dis-assembled your imaging rig).  If you have to take things apart every night and re-assemble, then you will indeed need to re-do flat frames every night.  Best time to do that is just before it's dark enough to image in the early evening, or just after it starts to get too light to image in the morning, so you don't waste dark-sky time doing flats.




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