Multi-Night Stacking

[-Joe_]

Hi,

Just wondering if there is a 'standard' process for dealing with multiple nights (maybe even separated by months) imaging and stacking.

e.g.

Imaging a DSO, I get 3 nights on the target, but separated by a few weeks each. All, say, Ha.

My current thinking is:

1. Produce flats for each session, darks & bias can remain the same (cooled camera)

2. Stack each session, with flats, bias & darks, to get a frame for the session

3. Stack the session frames to get the final stacked image

Or is there a better way?

The reason I'm not just stacking them all together is that the flats might change in between..

cheers

Joe

Edited August 1, 2019 by -Joe_

[Freddie]

Which stacking software are you using?

[-Joe_]

9 minutes ago, Freddie said:

Which stacking software are you using?

Good point, DSS. Happy to try something else if more suitable...

[happy-kat]

DSS is fine, best if the only variable is exposure length.

Use the group tab that gets exposed along the bottom for each set if the exposure length varies.

Calibration files can only be used once, see the DSS help file to see how calibration files are used with groups.

You could also try stacking each night separately with calibration files and then stacking the output files for a final.

[-Joe_]

Ahh, so thats what groups are for in DSS.

I guess the process is (given my example above):

Add darks & bias to Main group

Add night 1 lights & flats to group 1

Add night 2 lights & flats to group 2

Then let DSS do it's business and should have a final stacked image.

Hopefully will have two nights of Ha ready tomorrow morning to give it a try.

[happy-kat]

For details of what files go where have a look

Link here

[-Joe_]

1 hour ago, happy-kat said:

For details of what files go where have a look

Link here

Yes, that’s where I got the info from.

[Starwiz]

On 02/08/2019 at 02:59, -Joe_ said:

Ahh, so thats what groups are for in DSS.

I guess the process is (given my example above):

Add darks & bias to Main group

Add night 1 lights & flats to group 1

Add night 2 lights & flats to group 2

Then let DSS do it's business and should have a final stacked image.

Hopefully will have two nights of Ha ready tomorrow morning to give it a try.

If it helps, here's what I do........

Add the lights and run registration only, no stacking.

Note the sub with the highest score, so this can be used as the reference frame.  I rename this file and copy it to it's own location, so I can use it with Ha, OIII subs, etc.  Registration needs to be run again after renaming.

I also check all the other scores, so when stacking, un-tick anything below 300 before stacking, or if I'm using it for a luminance layer will un-tick anything below 1600 as I want the detail to be as sharp as possible.

In the other tabs, I add the subs from each night, each to its own tab.  You can re-use the calibration frames for each tab if needed, by copying them to separate folder locations.  DSS looks at the complete path, not just the file name to decide if a file is the same as a previous one already loaded.

If the calibration frames are in the first tab, they will affect all other frames regardless of which tab they are in.  If they are in another tab, then they only affect that tab.  So I put calibration frames into each of the other tabs and just leave the reference frame in the first.

If the reference frame is from Ha and I'm stacking OIII for instance, then make sure the reference frame is un-ticked before stacking.

John

Edited August 3, 2019 by Starwiz
Grammar correction

[retret66]

This is what I do. I create flats and calibrate each lights and put it aside, this helps lessen the disk space. I do not align or stack unless I need to show my work. Once calibrated, I label the folder like "Calibrated_mmddyy" and store the subs there.. Just create flats every morning when you are done each day, I tend not to use flats before imaging because dust spots may appear later on.