Stacking different exposures

[labtech1122]

Hi, I've got some data of a target I did with differnt exposures and wondered the logistics of stacking them together.

I know you can stack them and what to use but I've always wondered about your dark frames, how do you stack the differnt exposures but keep the darks with their matching lights so you don't calibrate say a 180s dark with a 300s light (as an example of course)

[vlaiv]

2 minutes ago, labtech1122 said:

Hi, I've got some data of a target I did with differnt exposures and wondered the logistics of stacking them together.

I know you can stack them and what to use but I've always wondered about your dark frames, how do you stack the differnt exposures but keep the darks with their matching lights so you don't calibrate say a 180s dark with a 300s light (as an example of course)

Provided that you camera can do that (and not all can, mostly CCDs are good at this and possibly some CMOS sensors) - you can scale your darks to do dark calibration with single set of darks.

You'd also need bias (it does not scale so it needs to be removed separately). There is "dark scaling factor" usually found in stacking software - and there you should use ratio of exposures. Say you want to calibrate 180s lights with 300s darks - you would use dark scaling factor of 180/300.

 

[Budgie1]

What stacking software are you using?

With DeepSkyStacker you can use the Group tags at the bottom and put each exposure set of lights, darks & flats in their own group.

In PixInsight it will distinguish between them and assign the correct darks to lights.

These are the only stacking software I've used, so the likes of Siril may do the same thing.

[vlaiv]

Oh, I've misread the question - you want to avoid what I've described above

Well, yes look at @Budgie1's answer above - usually there is a way to group lights with corresponding calibration frames

[labtech1122]

OK great, I'll give it a go on pixinsight, I started using siril because pixinsight can be a bit intense on the mind sometimes haha. I used to use DSS 2 years ago when I started but could never get it to work correctly but back then I was using a Canon on a very long focal length scope so now with the asi183mc pro and a 72ed I'm sure it will be easier

[Mal22]

A tip for Deep Sky Stacker - unless perhaps this “bug” was fixed and I didn’t get the memo… 

if you put calibration frames in Group 1 then they will be applied to all other groups, while from Group 2 onwards they will only be applied to the group they’re placed in. I usually just pop one light frame in Group 1 because it can’t be empty, and then Group 2 has all my lights/darks/bias etc from one night, Group 3 a different night etc etc etc. 

Of course if all your nights of data are the same exposure (and collected within the same year), you can just put one master dark frame in Group 1 and it will apply to all groups.

[900SL]

To do multiple exposure stacking in Siril, you need to write a script.

 

There's an excellent Siril tutorial series online by Rich of Deep Space Astro. Well worth running through

 

 

[Budgie1]

7 hours ago, labtech1122 said:

OK great, I'll give it a go on pixinsight, I started using siril because pixinsight can be a bit intense on the mind sometimes haha. I used to use DSS 2 years ago when I started but could never get it to work correctly but back then I was using a Canon on a very long focal length scope so now with the asi183mc pro and a 72ed I'm sure it will be easier

When stacking in PixInsight's WBPP, your dark-flat files just go into the "Dark" tab, then WBPP matches them with the Flats with the same exposure length or filter name (if using mono ). There isn't a separate folder for Dark-Flats.  

[alacant]

16 hours ago, labtech1122 said:

started using siril

Siril makes it easy.

Pre process each exposure set, copy (or use the conversion tab) the pp files to a new working folder.

Register

Stack

That's it.

Cheers and HTH.

 

Edited September 16, 2023 by alacant

[labtech1122]

On 16/09/2023 at 09:41, 900SL said:

To do multiple exposure stacking in Siril, you need to write a script.

 

There's an excellent Siril tutorial series online by Rich of Deep Space Astro. Well worth running through

 

 

I've seen this before, love his videos, he's taught me everything I know about siril haha. I've been using sirilic but there isn't a section for separate darks

[labtech1122]

On 16/09/2023 at 18:13, alacant said:

Siril makes it easy.

Pre process each exposure set, copy (or use the conversion tab) the pp files to a new working folder.

Register

Stack

That's it.

Cheers and HTH.

 

Oh ok, ill give this a go. So do I do the normal steps with calibrations on the lights for each set then register the calibrated lights all together?

[labtech1122]

On 16/09/2023 at 18:13, alacant said:

Siril makes it easy.

Pre process each exposure set, copy (or use the conversion tab) the pp files to a new working folder.

Register

Stack

That's it.

Cheers and HTH.

 

Also, how do you register 2 sequences together?

[AstroMuni]

2 hours ago, labtech1122 said:

I've seen this before, love his videos, he's taught me everything I know about siril haha. I've been using sirilic but there isn't a section for separate darks

If you split the different exposures into its own set, you can attach the different dark sets accordingly in SIrilic. i.e S1 could be (say) 30s lights, 30s darks, master flat, S2 60s lights, 60s darks, master flat etc. If you have taken the exposures on different days with changes to optical train then instead of master flats it would be flats taken on that day instead of a master. Hope this makes sense?

Edited September 25, 2023 by AstroMuni

[alacant]

4 hours ago, labtech1122 said:

how do you register 2 sequences together

Hi

That's what I described...

Let me know which bits need clarification.

Cheers 

Edited September 25, 2023 by alacant