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Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 3:48 pm
by Twisted Carrot
Hi all,

Can someone give me some advise on stacking together multiple exposure subs.

E.G.
20 x LRGB @ 300 seconds
20 x LRGB @ 180 seconds
20 x LRGB @ 60 seconds

Software I have is DSS, MaximDL & Pixinsight

Just need to know what the best process is to stack the different subs to get one set of LRGB to work with.

Thanks in advance

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 4:10 pm
by swag72
Sorry I'm being a bit thick........ do you have 20x30s L, 20x30s R, 20x30s G and 20x30s B and so on?

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 4:12 pm
by Twisted Carrot
Yes Sara

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 4:25 pm
by swag72
OK - Stack each set of data separately with your calibration frames..... so you end up with a stack of Luminace at 30s, Stack of red at 30s, stack of blue at 30s ...... etc..... You'll end up with a lot of different stacks!!

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 4:40 pm
by Twisted Carrot
Yes I've done that but what if I have a set of stacked 30s and a set of stacked 180s? How do I stack these together?

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 4:42 pm
by swag72
You don't...... You stretch them independently and then layer them in to match the appropriate areas.

Well that's how I do it anyway

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 6:38 pm
by Twisted Carrot
Sorry to be a pain.....so correct me if I'm wrong:-

So if I had a master luminance done from stacking 20 x 60s calibrated frames and I had 20 x 120s individual calibrated frames - would I add each individual 120s calibrated frame to the master luminance?

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 6:47 pm
by swag72
You should only add the same length subs to the one stack......

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 6:51 pm
by swag72
So you have your luminance master of 20x60s...... put that to one side.......now stack your 120s subs......... Now you have 2 stacks...

Re: Stacking multiple Exposures

PostPosted: Thu Dec 22, 2016 9:07 pm
by julianr
With Pixinsight the best way to combine them will be with the tool hdrcomposition - first off create you 3 master stacks of the each filter - 60s,180s 300s - save them (still linear stage) then enter dealing with each filter in turn - load the three stacked images in hdrcomposition eg 3 different exposures in luminance- then just hit the global apply - default settings normally works for most cameras

This tool will use the shorter subs for the star cores and longer stacks for the rest of the image

Hope this works - this method should give more dynamic range - once stretched it is normally worth doing hdrmultiscaletransformation to allow the full range to be seen