The Andromeda Galaxy - 3 Panel mosaic

[happy-kat]

As it was wide field I thought it would be less interesting
https://stargazerslounge.com/topic/3469 ... ion-mosaic
I haven't done a mosaic of a closer target to have experienced strong light intensity differences that M31 would give.
When processing repeats I like to use STReplay (a great utility) as it saves much time of reading log files.

[Stefan B]

Thanks! I see, that's really widefield! But it looks great, seamless stitching, awesome result. Maybe I give ICE a try during a cloud period

Clear skies!
Stefan

[bobharmony]

Thanks for the idea of using ASTAP to stitch the panels together while the data is still linear. I have been struggling with putting together my first mosaic, a 4 panel of the Cygnus Loop and hadn't figured a way to get the panels together without first processing them each individually in ST. Trying to keep differences in background and color cast from creeping in were very challenging. We'll see how some iteration of ASTAP works. Nice sharing, Stefan!

Bob

[Stefan B]

@bobharmony Great it was helpful for you. I'd be interested in the results and thoughts if you like to share them.

Regards
Stefan

[bobharmony]

Stefan - I am trying to follow the process you lined out using my Cygnus Loop data. I am able to load each DSS stack (4 for me) into StarTools and bin-crop-wipe to even out the gradient in each panel. There is no option to save the file as a .fts file, my best available choice is 16 bit .tif, or I could do 8 bit .png or .jpg. I tried with both .tif and .png and ran into issues with ASTAP.

When I load the files into ASTAP, it will not solve either format, and it creates a .fit copy to work on. It can solve the .fit files and stitch them, but ALL the nebulosity is gone when I look at the .fit file in either ASTAP or ST. The only thing that remains is about 40 of the brightest stars against a very black background.

My question is what format did you save the bin-crop-wipe output from ST as? I may need to look into whether I can control what ASTAP does when it makes the .fit working copy that might corrupt the data somehow. The nebulosity is there in the .tiff version that I view in ASTAP, so it looks like the conversion process to .fit is what screws things up.

Thanks for any insight you can offer!

Bob

[Mike in Rancho]

Hmmm. Well it would pretty much have to be the tiff save option out of ST, as that is the only thing reasonably viable.

How were the first stacks created, also in ASTAP?

Have you turned off convert OSC images to color? So that it is not debayering files that are already debayered?

I'll have to look to see what other settings might be an issue. Been a long time since I played with mosaic in ASTAP.

[Stefan B]

My question is what format did you save the bin-crop-wipe output from ST as?

I used TIFF. Just tried to stitch again and had the same problem. No solution found. Don't think that happened during my first try... I fiddled around a bit with the stitching parameters:

ASTAP stitching.JPG (69.14 KiB) Viewed 5557 times

This combination worked on my data. Changing downsample from 0 to 1 finally led to a solution. Whatever that means exactly. Anyway, this is what worked...

I found no parameters to influence the generation of the fits intermediate.

Have you turned off convert OSC images to color?

That's greyed out if choosing stitching mode

[Stefan B]

Maybe has something to do with the star databases and an ASTAP update? Found this on the ASTAP website:

https://www.hnsky.org/h18.htm

ANNOUNCEMENT:
ASTAP solver is now using new H17, H18 star databases. The stars are split in 1476 files of about 5x5 degrees instead of the usual 10x10+ degrees for the 290 files. The blind solving speed increases if your field-of-view is equal or smaller then about 1.5 degree. Blind solving speed doubles at a field-of-view of 0.5 degree compared with using the G18 star database.

There is no urgency to replace the existing G17, G18 databases. They will keep on working. In the long term I would recommend for field-of-view smaller then 1 degree to move to the H18. There is no penalty for using the H18 instead of H17, same speed only the size is larger and it goes deeper. If you install the new database, remove/uninstall the old one to activate the new one.

I'm still using G17. Haven't updated yet. But may be worth a try.

Regards
Stefan

[bobharmony]

Thanks, Stefan. I'm still using g17 as well. After pondering this a while longer, I went with what I used originally. I took the 4 wiped panels and loaded them into MS ICE for stitching. It didn't hesitate to produce a solution. I will post the result in my thread on the subject.

I had the same settings in ASTAP that you showed. If I get energetic I will try to change the downsample value form 0 to 1 and see if that produces a solution.

Mike, all stacking was done in DSS, ASTAP only came into the picture to attempt stitching the panels together.

Bob