Combining data from different scopes

Star Alignment works great for registering them

I wonder how to get the background lightness and color to match though, with different data

I tried getting some free data stacks from different people (including myself), of M63, to make a very long integration image, and after registering, easily saw the borders between the frames in the stacked image; it was so noticeable and I could do nothing about it; I redid my steps, this time tried LinearFit on all of the data stacks, stacked them, was no good; went back again, tried BGN, and Gradient Correction, and Automatic BG extractor, still didn't help; so I gave up and forgot about it.

Tried different settings in ImageIntegration too; like using LinearFit rejection vs no rejection vs Percentile, Median vs Average stacking, nothing helped as much as I'd like.

So I'll be listening to this thread.

This is what it looks like; not very appetizing:

(Median stacked, Percentile clipping; autostretched)

Star Alignment works great for registering them

I wonder how to get the background lightness and color to match though, with different data

I tried getting some free data stacks from different people (including myself), of M63, to make a very long integration image, and after registering, easily saw the borders between the frames in the stacked image; it was so noticeable and I could do nothing about it; I redid my steps, this time tried LinearFit on all of the data stacks, stacked them, was no good; went back again, tried BGN, and Gradient Correction, and Automatic BG extractor, still didn't help; so I gave up and forgot about it.

Tried different settings in ImageIntegration too; like using LinearFit rejection vs no rejection vs Percentile, Median vs Average stacking, nothing helped as much as I'd like.

So I'll be listening to this thread.

This is what it looks like; not very appetizing:

(Median stacked, Percentile clipping; autostretched)

Richard Carande:
What software are you using?  Sounds like PixInsight from the wbpp reference.  I do this in Astro Pixel Processor, and it just works, automatically resampling to the reference pixel scale, or another specified scale.  Not sure about how to do it in PI, which I also use occasionally.

Aris Pope:

Star Alignment works great for registering them

I wonder how to get the background lightness and color to match though, with different data

I tried getting some free data stacks from different people (including myself), of M63, to make a very long integration image, and after registering, easily saw the borders between the frames in the stacked image; it was so noticeable and I could do nothing about it; I redid my steps, this time tried LinearFit on all of the data stacks, stacked them, was no good; went back again, tried BGN, and Gradient Correction, and Automatic BG extractor, still didn't help; so I gave up and forgot about it.

Tried different settings in ImageIntegration too; like using LinearFit rejection vs no rejection vs Percentile, Median vs Average stacking, nothing helped as much as I'd like.

So I'll be listening to this thread.

This is what it looks like; not very appetizing:

(Median stacked, Percentile clipping; autostretched)

That's awesome.. star alignment gets them registered but does not combine them? So you would have to go and integrate the images? 

tried 2 with Average, no rejection, it gave this error:

"ImageIntegration: Cannot execute instance in the global context.

Reason: This instance of ImageIntegration defines less than three source images."

Aris Pope:
I know it can be done since I see all of these collaborations that have different scopes and cameras. How can I combine the data?

Álvaro Méndez:

Star Alignment works great for registering them

I wonder how to get the background lightness and color to match though, with different data

I tried getting some free data stacks from different people (including myself), of M63, to make a very long integration image, and after registering, easily saw the borders between the frames in the stacked image; it was so noticeable and I could do nothing about it; I redid my steps, this time tried LinearFit on all of the data stacks, stacked them, was no good; went back again, tried BGN, and Gradient Correction, and Automatic BG extractor, still didn't help; so I gave up and forgot about it.

Tried different settings in ImageIntegration too; like using LinearFit rejection vs no rejection vs Percentile, Median vs Average stacking, nothing helped as much as I'd like.

So I'll be listening to this thread.

This is what it looks like; not very appetizing:

(Median stacked, Percentile clipping; autostretched)

Unless someone else tells you a method that works in the software you already use, you can always try Astro Pixel Processor (it has a one month free trial) to do this. The Local Normalization process tends to blend these things when combining different stacks. You just add all the images (the minimum is 2 images) and integrate choosing Local Normalization. Start with 2nd degree, 4 iterations which usually works and go up from there if needed. Sometimes I’ve needed to use 4th degree but it usually works great with the 2nd. It matches the background intensities and blends the seams. The option “multi-band blending” supposedly helps with these but I havent had any good results with it although you might play with it too.

Jon Rista:

Star Alignment works great for registering them

I wonder how to get the background lightness and color to match though, with different data

I tried getting some free data stacks from different people (including myself), of M63, to make a very long integration image, and after registering, easily saw the borders between the frames in the stacked image; it was so noticeable and I could do nothing about it; I redid my steps, this time tried LinearFit on all of the data stacks, stacked them, was no good; went back again, tried BGN, and Gradient Correction, and Automatic BG extractor, still didn't help; so I gave up and forgot about it.

Tried different settings in ImageIntegration too; like using LinearFit rejection vs no rejection vs Percentile, Median vs Average stacking, nothing helped as much as I'd like.

So I'll be listening to this thread.

This is what it looks like; not very appetizing:

(Median stacked, Percentile clipping; autostretched)

I think you said you acquired these from different public stacks...

Looking at the result here, I would first question if each of these stacks were properly flat calibrated? The fields do not appear to be flat or uniform, and edge artifacts don't appear to have been cropped out of several of these either.

If the goal is to create the largest field possible from integrations from disparate sources, I would say that flat calibration and really calibration in general, would become critical. Even with good calibration, due to dithering, there is often going to be border/edge artifacts, and I would think you would want to crop those out first, before trying to combine all the individual registered integrations into a single integration. Flat calibration in particular, would need to be very meticulously don to ensure that the field was as clean and flat as possible. 

As for blending across the borders...there is bound to be some degree of difference between the individual integrations. You could give LocalNormalization a try and see if it is able to neutralize the differences between the backgrounds and eliminate (or at least minimize) the borders.