Deep Sky Stacker - Multiple Nights Data

[Startrek]

I regards to the correct method of loading your data and calibration frames in DSS which have been captured over multiple nights can someone provide some clear concise proven method.There is so much information and varying advice on other forums it’s ridiculous

Test Case Example for say M8 ( camera not touched and same temperature and focus for both nights )

Night 1
Captured 40 lights
Captured 40 Flats
Captured 40 Bias

Night 2
Captured 50 lights

My Understanding
Load Bias into Main Group ( as Bias is common for both nights and is just recording noise )
Load Lights and Flats night 1 into Group 1
Load Lights night 2 into Group 2

Or alternatively

Load Bias into Main Group
Load Lights and Flats night 1 into Group 1
Load Lights night 2 into Group 1

NB : Light frames both nights are not plate solved , only aligned visually using zoom box ie: visually as close as possible within say 10 to 15 pixels

Appreciate some good advice and comments on the above from users of DSS

Many Thanks

[xa-coupe]

My way... and probably the wrong way but so far it seems to work.


1. Get multiple nights of data.
2. Get dark and bias frames at some time (cooled camera makes timing unimportant)
3. Get flats (and dark flats should you use them) at the end.
4. Blend together in DSS.

[Startrek]

Jeff,
Thanks for replying
I found a link to the DSS forum to a post by David C Partridge who is one of the dedicated guys who took over development support of the DSS open source code in early 2018 for the benefit of us amateur astrophotographers
He described the best way to calibrate and stack using data captured over more than one night

Here it is .......

Stacking Multiple Nights Data in DSS

1/ Camera not removed over multiple nights
( same orientation, temperature and focus )

Load frames from multiple nights Lights , Darks, Flats, Dark Flats and Bias into Main Group then Check All
Register as normal and then Stack

2/ Camera removed after 1st night and re installed 2nd night and so on....( same temperature and re focused )
Must take new Flats and Dark Flats
Darks and Bias can be reused

Load all Darks ( Darks or Bias ) from multiple nights into Main Group and Check All
Load a single Light frame from night 1 into Main Group , right click and mark it as a “Reference Frame”
Leave this frame unchecked
Now load all your Lights , Flats and or Dark Flats from night 1 into Group 1 tab and Check All ( no reference frame required)
Then load all your Lights , Flats and or Dark Flats from night 2 into Group 2 tab
Register as normal and Stack

DSS will create and save a final calibrated Stacked image file ( FTS ) plus Master Dark , MasterFlat , Master Dark Flat and Master Bias files in appropriate file folder locations

I’ve also attached a PDF for convenience

Cheers
Martin

[xelasnave]

I found DSS extremely forgiving...using only light frames I have taken subs on different nights with half being "upside down" to the first batch...the overlap being so great that extreme cropping was required but DSS did not complain...I have posted this Lagoon Nebula some time ago but this was the most extreme example of subs being all over the place.
If you put dark frames in the mix I doubt if it would work however.
Slex

[AdamJL]

Lights from night one, and any calibration frames go into the main tab.
The next nights (lights + calibrations) go into the next tabs (so 3 nights will have 3 tabs).
If I'm using darks, they go into the first tab (so long as they match the other nights, if not, those tabs will have their own darks)
seems to work fine. That's how I stacked my recent Tarantula image

[Startrek]

Adam,
Thanks for your info
Is your camera left intact each night and using same focus , temperature and gain ?
If so, David the DSS developer advised you only have to use the Main Group tab or original tab and load everything in
If you move or remove the camera on any night , then option 2 in my post (his advice) is the correct way to calibrate and stack in DSS.
Remember darks and bias are only recording noise from the cameras electronics and are therefore common to any sub taken with same exposure time and gain etc.. they can be reused many times hence DSS makes a Master Dark or Master Bias for you to use

Cheers
Martin

[AdamJL]

Hi Martin

Well I dismount the scope from the mount and bring it inside. That sort of movement is enough to shift dust motes about. Knock some off, move others around.

The next night I'll setup completely from scratch again, including refocusing. And I'll take new flats. Therefore I separate the nights in DSS via the panels. Seemed to work okay on my recent Tarantula image.

[Addos]

you only need to use the groups in DSS if your multi night data requires a different calibration set.

calibration frames that are common to all nights (such as darks) should be loaded into the 'main' tab and it will apply to all subgroup frames.

really, you only need to split across multiple groups if you have different flats sets.

also dont forget to nominate a reference frame.