Can I stack different sized files?

[traveller]

Need some advice on stacking.
I did a couple of imaging runs of 47 Tuc recently. The first batch was done in late Nov had the target centred nicely, but the latest batch done on new years night did not have the target centred (it was at approx 7 o'clock position).
I tried to stack them but the new batch got rejected as I assume the target was way off for the images to be plate solved adequately.
My next attempt is to manually resize the latest batch to place the target in the centre so they can be recognised and stacked. So here are some questions I hope someone can answer:
1. Will this approach work? I would assume so, but not for certain.
2. Once I re-centred my latest batch, the file size will be smaller. Will that affect the stacking?
3. What format should I save my re-centred files? (currently in Canon Raw file, the late Nov batch is also in CR format)
Thanks!
Bo

[rustigsmed]

have you tried stacking the two end stacks together? or merging them in photoshop? then crop to suit?

[RickS]

What software are you using for stacking, Bo? It's a pretty busy field so I guess it's not surprising that it's giving you problems.

Cropping the subs to make them match more closely seems a reasonable approach if all else fails. It would certainly work in PixInsight and differences in size between subs wouldn't matter (by default they would all be registered and cropped/padded to match the reference image.) After cropping I'd probably save them as FITS files before registering them.

Cheers,
Rick.

[traveller]

Haven't tried that, but my assumption is to line up the raw files so they can all be done with stacking in one shot. Besides, my PS skills are not that crash hot :lol:



I am using Image Plus but also have Deep Sky Stacker. I will save the new batch as FIT files and keep the late Nov batch as CR files.
Thanks again
Bo

[traveller]

one more question, can I automate the cropping process or do I need to crop them individually? (only 20 frames)

[rustigsmed]

have you tried intersection mode and selecting a 'good' orientation frame as the reference frame?

[traveller]

Sorry Rus, you need to dumb down that a bit for me :)
Do you mean using the grid patterns in the crop function to get a reference frame and then copy that position for each subsequent frame?
I am doing that.
Bo

[traveller]

Can't save as FIT files in Photoshop :help:
The only option is to save as a TIFF or Photoshop RAW file.
If I save as TIFF, I can choose between Interleaved RGBRGB or Per Channel RRGGBB, which should I choose to match the Canon bayer matrix? :thanx:
Bo

[RickS]

I wasn't sure what software you were using to do the crop. Only astro software usually understands FITS format. Can't ImagePlus do cropping? I have used it in the past but it was a long time ago...

Anyway, TIFF is probably OK. Interleaved is the more standard format but you should probably write a test file and see if ImagePlus reads it OK. The RGBRGB/RRGGBB setting is unrelated to the Bayer matrix in your camera. It determines if the the data in the TIFF file is saved with RGB data mixed or separate (all the R, then all the G, then all the B).

Cheers,
Rick.

[traveller]

Update:
I cropped the files (14 down to 12 MB) and attempted to stack them using Image Plus - fail :sadeyes:
I got a warning stating the files must be same size so the 20 new photos didn't stack.
Rustigsmed has kindly offered some assistance, so I will follow that up now.
Thanks all
Bo