Combining subs (& flats) from different imaging sessions

[OutThereSomewhere]

Hi,

I'm sure that this must have been covered elsewhere, so I'd appreciate a link to wherever that may be, if someone would be so kind. Or if not, could someone please post some help?

My problem is that I took a set of 600s Ha subs of the Heart nebula at the Galloway star party some months ago - but not enough for a nice image. So last night at home, I took another set of subs - same exposure and Ha filter. I took flats on both occasions, but the dust bunnies are bound to be different on each set.

My question is: How can I combine the subs from both nights (taking into account that I have two different sets of flats)? Just stacking the two final outputs (one from each occasion) doesn't seem right if the idea is to put lots of subs together in one single stacking "operation" in order to reduce noise.

I use Maxim DL, Astroart and Photoshop 5 and confess to have "all the gear, with no idea"!

Thanks!

[andrewluck]

Calibrate the sets of subs from each night separately using the flat frames you took on the night for each set. Once that's done, then stack the calibrated subs from both nights in one operation.

Andrew

[Mik3]

Is there anyway to do this in DSS?

[Josh Wilson]

DSS should automatically align the images with the assumption that the images are offset by mere arcseconds, too small for the human eye to see. Have you tried stacking them yet?

Josh

[andrewluck]

Not sure about DSS as I haven't used it. The OP has Maxim which is easy to use for this type of task. Provided the images can be plate solved, it will stack based upon the astrometric data which can help if it can't match the stars in the images.

Andrew

[OutThereSomewhere]

Andrew,

Thanks for the advice. It now seems so obvious. I can't understand why I couldn't work that out for myself!

I'll give it a go now. Thanks again!

[Freddie]

Mik3 and Josh talked about DSS. You can use DSS for this but you can't just load them all up, you need to put the different sessions into different groups (tabs at the bottom of the screen). First group is "main group" then they are numbered "group 1" etc.

[cp255]

Just put each set of lights and flats in a different group using DSS. DSS will create a master flat for each group and only apply it to the lights in that group.