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How to improve stacking with shaded images that have a high-contrast edge


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Hi,

I'm trying to align several hundred images of the recent Lunar Eclipse.

Affinity Photo does an absolutely AMAZING job on most of them ... images where the Moon is full are aligned almost perfectly.

But - other images where parts of the moon are in shadow do not get aligned well at all, even though there is a very bright, sharply defined edge on the opposite side.

Apart from aligning layers manually, what can be done to improve automatic alignment when there is a region of high-contrast, like the bright edge of the moon against the black background of space ?

Gary

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Hi Gary - without editing the image I don't suppose there's much that can be done without us drastically changing something. 

Do you want to attach a few examples? I'm not proposing you send over hundreds of images but perhaps a few that work and a few that struggle.

Private Dropbox folder if you wish to upload some - https://www.dropbox.com/request/be1EFy5FGTzxwNS6yAJG

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Hi Chris,

Many thanks for your reply ...

Ive added some FITs to your Dropbox ... they will make more sense if you take a look at this post first :)

In a nutshell, AP seems to 'try' to align the first 403/698 images.
The alignment is far from pixel-perfect - to get best alignment I have to align each layer manually.

Then the 404 th image is way off - almost half the width of the moon.

I suspect this is because the moon changes a bit with each image as the shadow of the eclipse gets larger.
AP could cope with images 1-403, but image 404 is just too different to image 1 to enable a good alignment.

After that, images are 'sort of' aligned in clumps.

It would be really helpful if you could respond to the post above, which has a lot more detail of the problem.

Best regards,

Gary

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There's a huge jump between the moons position in those images you uplaoded - I'm not sure how much we should force the alignment. I'll get it over to the developers. 

On 8/2/2021 at 6:48 AM, Gary.JONES said:

Apart from aligning layers manually, what can be done to improve automatic alignment when there is a region of high-contrast, like the bright edge of the moon against the black background of space ?

This is down to the app - so a programmer would need to look at this. 

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Hi Chris,

Many thanks :)

Actually, AP has presented no problems aligning star fields that are much further separated than these shots of the moon - it even aligned 2 sets of images taken across the meridian, meaning one set was upside-down compared to the other.

The thing that makes aligning star fields less challenging is that they are the same from image to image - just displaced horizontally / vertically.

The thing with the moon (and planets) is that they rotate from frame to frame, so they are fundamentally different to star fields.

The eclipse is a special case - the moon changes shape over time as well as rotating :)

If AP could be made to align on a set of user-defined edges or points (eg craters), that should work.

Regards,

Gary

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