Stacking Multiple Stacks?

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poolemarkw
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Stacking Multiple Stacks?

#1

Post by poolemarkw »

Does stacking multiple stacks yield the same result as creating one stack of the total number of frames? For example, suppose that I create a live stack of 100 frames tonight and save as a 16-bit FITS file one evening, then create a live stack of 200 frames of the same image on another night. If I then used Deep Sky Stacker to stack the two stacks into one stack, is the resulting final stack the same result as one 300-frame stack?

What I'm wanting to do is to get data over multiple nights but avoid having to save all of the individual frames and stack the large group later.

Thanks,

Mark
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turfpit
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Re: Stacking Multiple Stacks?

#2

Post by turfpit »

Mark

See viewtopic.php?t=561

Dave
poolemarkw
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Re: Stacking Multiple Stacks?

#3

Post by poolemarkw »

Hi Dave, I don't believe that the link that you referred me to answers the question.

thanks,

Mark
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admin
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Re: Stacking Multiple Stacks?

#4

Post by admin »

Hi,

If all your stacks are the same length then the answer is yes. If your stacks are different lengths then I suspect it may be hard to persuade deep sky stacker to give additional weight to the longer stacks in the way that it should, which will mean that some of the additional detail that should be visible in the longer sub stacks won't be given the weight it deserves in the final image.

Cheers, Robin
poolemarkw
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Re: Stacking Multiple Stacks?

#5

Post by poolemarkw »

Excellent, thanks Robin!

Mark
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Calamity_Jane
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Re: Stacking Multiple Stacks?

#6

Post by Calamity_Jane »

I can report that stacking multiple live stacks in Siril works just fine. I don't know whether it weighted the images by integration time, and can't say that I really much care as the stacks were all 3-4 hours.

I was primarily interested in tracking the very faint stars around the M51 A&B pairs of galaxies (NGC 5194 and 5195). The negative I made from the resultant picture shows that I was more successful than I had hoped for a total of 15 hours exposure.

(11" SCT, 0.63x reducer/corrector, ZWO ASI2600MC, four live stacks in SharpCap, Siril for overall stack, photometric colour calibration, etc, and Gimp for final processing.

M51 Jan 23 15h Negative 2.jpg
M51 Jan 23 15h Negative 2.jpg (918.08 KiB) Viewed 414 times
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admin
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Re: Stacking Multiple Stacks?

#7

Post by admin »

Hi,

that's quite a different approach to the processing, but *very* striking - you could imagine that you are looking at a pair of black holes!

Glad to hear that the stacking worked as expected.

cheers,

Robin
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Calamity_Jane
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Re: Stacking Multiple Stacks?

#8

Post by Calamity_Jane »

Hi Robin,

I nicked the idea from the way they used to show galaxies in the era of photographic glass plates. Arp's 1966 Atlas of Peculiar Galaxies is available for free online, and that's the way the galaxies are presented there. See e.g. http://ned.ipac.caltech.edu/level5/Arp/Arp22.html

Regards,

Jane.
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