How to stack across multiple sessions

[widotje]

Hi there,

I've collected rgb (narrowband) images across multiple sessions with some months in between. I've already created a stacked image for each session. Would it be wise to combine the already stacked image with a second stacked image, or should I just use the individual images, put them into multiple groups,  to create a new stacked image? Happy to hear your thoughts on this. 

 

Wido.

[PhotoGav]

Good question, personally I would use APP in multi session mode to make stacks from all subs per filter. I would take care to ensure all calibration frames are correctly assigned to their appropriate sub sets. Whether better results are obtained from stacking all subs in one go versus stacking stacks is not something I know the answer too... interested to hear what others think.

[alan potts]

I use Deep Space Stacker and you can stack different; exposures, speeds and different nights. You load you first set in with Darks, Flats etc, then look at the bottom of the display and you will see the Tab Main Group, this is where Darks and Flats go with you first group of captures. As soon as you enter this the Tab Group 1 will show up next to main group, in this only enter the next night of speed/ diff exposure, no Darks etc. As soon as this is entered Group 2 will shoe up and so on and so on.

I have evn stack different ISO in one group and it handles that fine too, and it's free.

Alan

[don4l]

This subject came up recently and @vlaiv explained why it was better to stack in a single operation.  I did an experiment and the single stack came out visibly better.

From now on I will only be doing a single combine.  My stacking software "CCDStack" seems to allow for differing exposure lengths and it also seems to cater for differing quality.

I couldn't get my head around the maths, but the difference on the screen was obvious.

[PhotoGav]

4 hours ago, don4l said:

I couldn't get my head around the maths, but the difference on the screen was obvious.

As astronomers, we love observational evidence!

[steppenwolf]

I'm a great believer in stacking all the images at once even if I do have a series of individual stacks already done from previous sessions - I have always felt that the images were better this way.

[wimvb]

Throwing them all into the pot is better, it gives a better average and pixel rejection is more "reliable".