Mosaic again: why don't these two images work?

[Nocturnal]

Hi Juan,

can you please take a look at the two images I've uploaded (uploading as I type this)? I'm trying to stitch together the Mosaic image as the reference and add the GSC one. I created a mosaic of these images before but the backgrounds were quite unmatched so I started fresh. Now the GSC one won't register. I can see the matching stars quite easily so I must be doing something wrong. Can you help please? Thanks!

Upload to the ftp server should finish in about 20 minutes.

[Juan Conejero]

Hi Sander,

Yes, you can make a mosaic with these images:

http://forum-images.pixinsight.com/legacy/mosaic-sander/01.jpg

Note the enabled "Use scale differences option". With these settings SA's RANSAC routine finds 29 matched star pairs, which is fine. However you can improve this to 48 star pairs by selecting 1000 maximum stars and 32 triangles per star. You can improve it even more by setting scale tolerance to 0.025. With these settings RANSAC finds 75 star pair matches out of 306 putative matches

[Nocturnal]

Hi Juan,

great, I'll have to give it another try with your suggestions. Like I said, I could get it to work once but not a second time after stretching the images a little to try to match the backgrounds a bit more.

The URL didn't work for me though but I believe you so it's no big deal.

[Nocturnal]

With the provided options adding the third image worked fine. Then I couldn't add the fourth. If I first added the third and fourth I could create a mosaic with images 1 and 2. One of the problems I noticed was that once I removed the <auto> from the number of stars field I could not restore it. Entering text is not allowed, leaving it blank simply brings back the previous value.

Anyway, it seems that for large mosaics like this it would be helpful to provide star alignment a hint. Indicate where you think the image should go and that's where the algorithm does its magic. I imagine it would be possible to draw a rectangle on the reference image where you expect the match to occur. This could cut down the number of stars dramatically. Perhaps a way to implement this would be to allow previews as 'focus selectors'.

Anyway, this is impressive stuff. Fun to play with.

[Juan Conejero]

Thanks

In fact, StarAlignment isn't intended as a mosaic generation tool. DA's mosaic generation feature works well, but wait to see what I have in mind. It will be a dedicated mosaic generator with interactive functionality, more or less as you've described