Blend together multiple images

[MrMxyzptlk]

Hi!

I have some pretty bad Orion Nebula data from last December (just about my third astro photo try), but I tried something different there: knowing the bright core of the Nebula, I made two sets of exposure: some 118x120s ISO3200 for the outer part of the nebula, and same amount but with 20s for the inner core. I thought I will reprocess with startools but I confronted with a problem: I had some drifting with the inner core, and that drifting was not visible on the exposures, but it becomes evident on the process, as I have to crop away almost half of the image because of stacking artifacts, and than I got a 4000x2000 pixel image for the whole nebula and I got an image of 3000x1500 for the core. In that moment I cannot get StarTools to join the two images because it says to me when I'm trying to load the second image that the two images don't have the same pixel size (Dimensions differ from already loaded file). Is there some options I'm overlooking? Even though I really don't care for this image, this could become a problem in the future too because I'm using dithering on my exposures, and I always get stacking artifacts so I will not have neither the same pixel size of the two image neither will I have the DSO exactly on the same place. Could there be made an implementation of some auto aligning the layers based on star positions even though the two images aren't exactly the same size nor the DSO is covering exactly the same part in the two image, and I should crop away the bad part of the image at the end (if there is such a place)?

Thank you

[admin]

Hi!

I have some pretty bad Orion Nebula data from last December (just about my third astro photo try), but I tried something different there: knowing the bright core of the Nebula, I made two sets of exposure: some 118x120s ISO3200 for the outer part of the nebula, and same amount but with 20s for the inner core. I thought I will reprocess with startools but I confronted with a problem: I had some drifting with the inner core, and that drifting was not visible on the exposures, but it becomes evident on the process, as I have to crop away almost half of the image because of stacking artifacts, and than I got a 4000x2000 pixel image for the whole nebula and I got an image of 3000x1500 for the core. In that moment I cannot get StarTools to join the two images because it says to me when I'm trying to load the second image that the two images don't have the same pixel size (Dimensions differ from already loaded file). Is there some options I'm overlooking? Even though I really don't care for this image, this could become a problem in the future too because I'm using dithering on my exposures, and I always get stacking artifacts so I will not have neither the same pixel size of the two image neither will I have the DSO exactly on the same place. Could there be made an implementation of some auto aligning the layers based on star positions even though the two images aren't exactly the same size nor the DSO is covering exactly the same part in the two image, and I should crop away the bad part of the image at the end (if there is such a place)?

Thank you

Hi,

An alignment procedure for the Layer module is planned for 1.4 which is a while away, so right now your best bet is to crop both images to the same dimensions (which is easy if both images start off the same size - crop will remember the settings you used). After that you'd use the offset filter in the Layer module.

That said, aligning is really a pre-processing procedure and DSS (or any other stacking tool) should have no trouble aligning two different stacks of images; just use one as a reference for the other, and your two exposures should be perfectly aligned, stacking artifacts or no stacking artifacts!

[MrMxyzptlk]

Thank you. I never thought to align the two images once again with a stack software. I always used Photoshop. I will try that, thank you