Author Topic: Mosaic formation in PI - What on earth is this?  (Read 3621 times)

Offline swag72

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Mosaic formation in PI - What on earth is this?
« on: 2013 July 09 13:31:02 »
Once I found a video on how to merge a mosaic in PI I was full of hope. It all seemed fairly easy and straightforward. Sadly, I've ended up with something of a mess and I don't know why. I'm hoping that someone recognises the issue or at least knows how I can make a start on fixing it.



On the right is the stack of subs, with histogram transformation and nothing more. The stars are not an issue at this stage. On the left is the same area, but after the whole mosaic process. As there are no issues prior to the mosaic stage, I think this isn't a calibration process.

Can anyone help me with this? Have you seen it before? I need to try to address it as the more processing goes on, the worse it gets.

Offline pfile

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Re: Mosaic formation in PI - What on earth is this?
« Reply #1 on: 2013 July 09 15:28:57 »
those are interpolation artifacts. it's ringing caused by the default interpolation method in StarAlignment. there's a clamping threshold slider you can adjust to try to mitigate this, but you may have to change interpolation methods to get rid of it. bilinear does not suffer from this artifact but the results are not as sharp.

Offline swag72

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Re: Mosaic formation in PI - What on earth is this?
« Reply #2 on: 2013 July 09 23:30:49 »
Thank you very much for that - Looks like I'll have to play with the settings then. I assume that it is at the stage where the individual panes are registered to the main mosaic reference that has previously been made?

Offline pfile

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Re: Mosaic formation in PI - What on earth is this?
« Reply #3 on: 2013 July 10 07:22:27 »
yeah, it can happen any time you have to register one image to another.

Offline swag72

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Re: Mosaic formation in PI - What on earth is this?
« Reply #4 on: 2013 July 11 04:58:50 »
Brilliant - I used Bilinear, perhaps losing a little sharpness but on a 3x2 mosaic, no matter. Then adjusted the feather settings to 23 in the GradientMosaicMerge tool and the job was done. A big thankyou - I was tearing my hair out with it and really didn't know what to do to sort it  :)

Offline pfile

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Re: Mosaic formation in PI - What on earth is this?
« Reply #5 on: 2013 July 11 08:06:49 »
no problemo, is this the sh2-129 image?

Offline swag72

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Re: Mosaic formation in PI - What on earth is this?
« Reply #6 on: 2013 July 11 13:36:57 »
Yes it is - a 2x3 mosaic with some rather faint signal!!