How to stack multiple nights pics

[paul101]

Hi all

I was wondering how to stack pics from multiple nights etc

I use dss and gimp.

Would I stack each night separately then stack the resultant pic from each night together or stack all pics from all nights together at once?

The other question is, how do I stack sets of images with different iso's and exposure times.

Also what method would I use to stack narrow band filtered images with different filters ie ha and oIII, and merge them together.

I am getting good with processing now just not sure of the above, I have just got up and running with a guided setup and want to get pics over a few nights.

Thanks for your help

Paul

[Freddie]

For the images from different nights and diffrent settings you can pop them all into DSS in one go.

For the different filters, you will need to stack each filter as a separate stack and then combine each stack in PS using chanels, not sure how that is done in GIMP

[dph1nm]

not sure how that is done in GIMP

Much the same I imagine - just put the b/w images into separate layers, colour them up as required using the curves tool, then use the additive combine layers mode.

NigelM

[paul101]

Hi

Thanks for the help, I will try this as soon as crappy weather turns better!

[jgs001]

There's a simple way in DSS... if you dump them all in together, then any calibration frames will be applied to all the images, and flats and darks may not fit properly. When you add any sort of frame to the list in DSS, a new group will appear along the bottom edge. Each group will only apply the calibration frames from that group to the images within it... therefore, put all the lights, darks and flats from night 1 into group 1 (remember you have to add a file of any sort into the master group, you can remove it after of course). Then add night 2 into group 2 (which will appear when you add a file to group 1. If you have any calibration frames that need to be applied to every image in all the groups (bias frames for instance), then you can just add that to the master group, and that will be used against each group as they are processed.

[Robd]

As HJohn says. If you want to stack different exposure lengths you can select 'Entropy Weighted Average' in the stacking parameters.. I have tried this but was not impressed with the results. Perhaps the range of exposures was too great.

Rob

[jgs001]

I've only tried entropy weighted he once Rob... I had 13 hours worth of data and it gave the best result of the stacks... the key is to keep the calibration frames with their specific data sets, after that use whichever stacking mechanism works best. I normally use a Kappa Sigma stack...

[paul101]

Thanks for all your info it's handy to know. Just need some good weather now!

[Uplooker]

(remember you have to add a file of any sort into the master group, you can remove it after of course).

Hi John / jgs001,

Would please clarify what you mean by this, what file?

regards,

Uplooker

[dmahon]

You need to put a file in the master group to open up the other groups.

Any calibration files in the master group will be applied to lights within all the other groups - if you don't want this to happen, once you have put something in it just to cause "group1" to appear, you can put something into group1 and then remove whatever you put in the master group list.

The one thing I annoying is that you can't apply calibration files to multiple groups - it either all or one. If you want to apply them to five groups out of six, you have to copy them so you have five seperate sets of the same calibration frames. Some sort of subgroup systems would sort this out.

[Uplooker]

Thanks dmahon. I had not noticed the "groups", obviously not looking.

Thanks also to paul101 for asking this question. I was sure I had seen it answered on here before but could not remember the answer.

I am waiting to get more data on M81 & 82, only got 2 hrs so far, and will need to stack all fromes.

Thanks all again.

Uplooker