Cygnus Loop - 4 panel mosaic

[Stefan B]

Hi Bob!

Great result! Looks like replacing Astap with ICE worked nicely! Did I get it right that you stitched linear data in ICE? I used ICE only once but I remember that you have to do the overlay manually, right? How do you do this when you basically can't see anything since data is linear?

Regards
Stefan

[bobharmony]

Hi Bob!

Great result! Looks like replacing Astap with ICE worked nicely! Did I get it right that you stitched linear data in ICE? I used ICE only once but I remember that you have to do the overlay manually, right? How do you do this when you basically can't see anything since data is linear?

Regards
Stefan

Thanks, Stephan. Yes, I used ICE to stitch the linear data I got after wiping the individual tiles. And you are correct, there is nothing visible in the ICE screen. I used the automatic stitching feature that ICE has available. Because I had already gone through the process of stitching together the fully processed panels (way back at my original post) I knew how much to rotate the stitched linear result. I was then able to Autodev in Startools and crop the rough edges.

This latest result looks a bit grainy to me, I am thinking about going back to square one and re-wiping the original panels with a much lower gradient % to see if I can clean that up. The original subs didn't show much gradient, but my flats didn't correct the vignetting completely, so I used Wipe to remove that. I think finding a way to clean that phase up will be useful.

I took your suggestion on setting the "downsample" and tried all 4 available values. Still no luck with platesolving, so no stitching is possible with STAP yet. I also just re-read your comment about the dark anomoly filter to a higher value (I used 3 where the luminance data stopped changing) and may give that a run as well.

It is all a learning process for me, and I am getting to understand ST better as a result.

Bob

[bobharmony]

Cool! Hard to tell though, it's reversed and I think a bit less stretched?

I went hunting for my folders where I did that mosaic, turns out February so a good ways back. I know I have a yellow pad with notes all over it too, but that'll be hard to find right now (I have lots of yellow pads lol).

But I was able to reconstruct a few things by looking at the interim files in various subfolders. The original FITS (from Eyal/Imtl on CN) were stacked in PI. I actually used Gimp, not ST, for my strategic cropping of these FITS files prior to doing mosaic in ASTAP. Though I may very well have AutoDev'd them in ST first in order to help get the precise pixel/resolution numbers for those crops, then took those numbers over to Gimp, which can save in FITS.

I gave it a re-test just now and ASTAP still stitched them together just fine. Albeit it was a huge nearly 1GB file surrounded by massive black space that would itself then need major cropping. And while ST (on my laptop) did take a good long while thinking about opening this 1GB FITS, it eventually did so and even managed an AutoDev, which looked pretty normal to me.

Gimp can scale also, if necessary. I think I note you say you used bin in ST for some of the pre-stitching prep.

Have not yet tried out an ST-saved tiff to see how that might work/not work as two of you are now saying. ASTAP is famous for turning everything into FITS files, and I suppose it does that here too? That said DSS is also handy for doing TIFF to FITS conversions, and allowing various types (16/32 bit), in case that is what is throwing off the results. Unsure, would have to test.

Thanks, Mike. Lots of good things to consider here. I hadn't thought about using DSS to change the files back to fits after saving them as 16 bit tif in ST.

It is interesting that ASTAP creates that huge black border around everything when it does the stitching. I have tried tweaking the FOV settings with no impact so I'm not sure where it is coming from. The file size does tend to choke my PC until I crop most of it away and save it to load into ST.

My cropped mosaic comes in at about 1G and ST doesn't have any issue dealing with it. The one with the black border intact weighs in at about 4G, and that is too much for the PC to handle.

Bob