Author Topic: Gradient Merge Mosaic error message  (Read 528 times)

Offline alcol

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Gradient Merge Mosaic error message
« on: 2018 February 05 12:26:59 »
Hi Folks help required.

I have been successful in the past with mosaics but I seem to have run into trouble with the 4 part HA Rosette nebula. I have cropped the 4 integrated images and ran through the mosaic process (in fact 2 or 3 times) all seems well until I put the images into the Gradient Merge Mosaic tool and it gives me a message "Error: Current image width differs from first image width.
<* failed *>
Checking the 4 image sizes I get 8445 x 6302  8445 x 6301  8446 x 6301  and 8445 x 6301  before starting the mosaic process all 4 images were identically cropped.

Anyone any idea where the process may have changed the image sizes? I followed Kayron's tutorial at http://www.lightvortexastronomy.com/tutorial-preparing-a-mosaic.html

Thanks

Offline John_Gill

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Re: Gradient Merge Mosaic error message
« Reply #1 on: 2018 February 05 23:52:19 »
Hi,

GMM does not use any image sizes when creating the mosaic, so perhaps you are using the incorrect images that were not SA .... perhaps someone else can help.

Look up
John
APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
Canon 60Da & ZWO1600mm
... when there are no clouds ...

Offline alcol

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Re: Gradient Merge Mosaic error message
« Reply #2 on: 2018 February 06 01:31:44 »
Hi John
These are the images that have the black areas in and contain the mosaic part and show its position in the overall mosaic. The measurements I have quoted are the size of these images, they are indicated in the process window when the images are opened.

Not sure why these very slight differences occur but I have found a way round it by opening the 2 images (in the 4 I quoted) and cropping 1 pixel off the 6302 measurement and 1 pixel off the 8446 measure. The 4 images are then the same size at 8445 x 6301 and are loaded into GMM and the mosaic is produced, no joins showing or pinched stars.

I have to say, it has worked without a problem in the past, so I'm not sure how 2 of the images gain an extra pixel, one in width and one in height.

Offline John_Gill

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Re: Gradient Merge Mosaic error message
« Reply #3 on: 2018 February 06 02:35:09 »
That is a strange issue.  I have cropped overlapping images that are being used in a mosaic without encountering the "size" problem when doing the SA and GMM...

Look up
John

APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
Canon 60Da & ZWO1600mm
... when there are no clouds ...

Offline John_Gill

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Re: Gradient Merge Mosaic error message
« Reply #4 on: 2018 February 06 06:26:13 »
mmh, I just got the same error, but found the error of my ways ...

Because you are doing a 4 panel (or bigger) mosaic, you would first create the "Template" file, doing a SA with "Register/Union Mosaic, then again using SA, with the "Template" as a reference you do a "Register/Match Images", this will create the 4 registered images.  These 4 new images are then processed with GMM.

I left out the "Register/Match Images" process and PI then complained about the differing sizes of each image.

Look up
John
APM 107/700 apo on CGX mount
ZWO Optics - Autoguiding
Canon 60Da & ZWO1600mm
... when there are no clouds ...

Offline alcol

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Re: Gradient Merge Mosaic error message
« Reply #5 on: 2018 February 06 08:53:21 »
Hi John

pretty sure I followed the process, as per your note, to get to GMM

Regards
Alec