Building First Mosaic - Several Failures in SA and Gradient Merge Tool

[georg.viehoever]

Why is it necessary to straighten the boarders? I hope I did not miss anything, because on my system there was no sound with the video...
Georg

[Hytham]

Juan,

Thank you very much for the video and it helped shed light on something that had always racked my brain;  I had absolutely no idea that I could black out all the pixels using the crop tool and pixel math.

Thanks again.

Georg,

My guess for straightening the border is to prevent any bright stars from appearing directly on the seams which would ultimately affect the visual appearance of the final mosaic.

[Andres.Pozo]

Juan,

Thank you very much for the video and it helped shed light on something that had always racked my brain;  I had absolutely no idea that I could black out all the pixels using the crop tool and pixel math.

This would have been done much easily using a paint tool.

[Tom OD]

Here is a screen shot of a left and a right panel that I tried to stitch together (each side is a top and bottom panel stitched). On the left in the screenshot, is the 4 pane result where I registered the left side to the right side. Both sides were mosiac'ed with the distortion selected. On the right hand side is the same 4 pane result but the left and right sides had the line straightened and the crop tool used to set the pixels outside the crop to black. As you can see there is a terrible result v excellent result using Juans method. Next I need to add in more panels to see how far can you go with this method.
Tom.

[georg.viehoever]

Tom,
the contributing images in the left example seem to have aliased borders. Zoom into those images and see if you have a direct transition between black and image pixels (which is needed by GMM), or if there is a gradual transition. If there is a gradual transition, increasing the GMM "shrink" parameter should help.
Georg

[papaf]

Albeit a bit complex, this produced wonderful results on my M31 mosaic too!
What's the secret here? Is it the straight borders?

[Tom OD]

So the next question is, if doing a bigger mosaic is there a formula to get the crop tool to set pixels to black on a 3x3 mosaic with one corner missing. Or other msoaic shapes that you might get. I only ask because if I tried making 3 strips of 3x1, the rotation and overlap may get to the point where if I straightened the strips you might cut off too much of the other panes and leave a gap in the mosaic. I have not put together a bigger than 4x4 yet with this method Juan outlined. I'm still playing about with the equation for slopes