A difficult mosaic

[LorenzoM]

Hello everyone!
I have a small problem about a two frames mosaic. I was wrong with frames in acquisition and the overlap is really small, just a few stars, that i have to choose manually.
Using star alignment tool the software doesn't find a sufficient number of stars.
How can i create this mosaic?

Thank you!!

[LorenzoM]

Sorry i have forgotten to give information about orientation.
The first image is connected to the second on the left side (right side of the first).

[pfile]

just make previews over the areas where they overlap...

[Juan Conejero]

Hi Lorenzo

You can make more difficult mosaics with SA As Rob has pointed out, with two previews roughly covering the overlapped areas this mosaic works without problems:

Click to view actual size

[LorenzoM]

Yes was very easy 
but now i have just two questions. In the video tutorial about mosaic i see he works with non streched images, using only screen transfer function.
Does not work in this way, to succeed i need to work using two stretched images with histogram transformation otherwise appears error "unable to find an initial set of putative star pair matches".
Second, in tutorial i have seen the way to use pixelmath to adjust different signal between frames, but is there a way to do this in automatic?

[pfile]

for your first question, i'm surprised at that because StarAlignment seems to work fine against linear, unstretched images, at least for me. then again my stars are always saturated so that might explain that. there are star detection thresholds in the StarAlignment tool that you can change. i've never had to change it but i suppose the sensitivity control is relevant.

on the 2nd, the LinearFit process can do a pretty good job preparing mosaic panels for merging.

[LorenzoM]

Yes, it's strange but works in this way. With unstratched imaged doesn't work.
If you want to try, here there are links to original fits, just calibrated with bias, dark and flat.

http://dl.dropbox.com/u/59547074/Public%20Fits/BarnardLoop.fit
http://dl.dropbox.com/u/59547074/Public%20Fits/LDN1622.fit