Assembling mosaics?

[AstroViking (Steve)]

Hi all,

After last week's trial run of a 2x2 mosaic/panorama of the Eta Carina nebula I went out on Sunday and tried again. Overall, I captured 4 hours worth of data (1 hour per panel) and am now trying to put things together and get a workable image.

My workflow so far has been to stack then apply a background extraction, green noise removal and a histogram stretch with SiriL 1.0.6 - all with the default values - and exported as a 32-bit TIFF. Each panel is then (I assume) roughly the same in terms of colour and exposure.

The hard part is aligning the 4 panels into one image. For the trial run I used Affinity Photo's Panorama mode and it worked without a hitch, giving me an aligned and (apparently) colour matched image to work on.

For some reason, Affinity is refusing to play along with the new images and only managed to stitch 3 panels together into an 'L' shape and would not add the fourth panel. I tried aligning it by hand but gave it up as a bad job after battling it for what seemed like ages.

For those of you who do mosaics and panoramas, what is your workflow and how do you stitch the panels together?

I've been tempted to try tools such as PixInSight or AstroPixelProcessor but have never really bothered because the tools I have work well enough for my skill levels. If it means a step up in terms of tools and learning then it might be time to make that step.

Many thanks,
V

[Nikolas (Nik)]

I use Astropixel processor as some of these third party apps just don't do it as well.

[ronson]

I haven't done a mosaic, but read people use the free Microsoft ICE with good success. The app is pretty old and no longer available for download from Microsoft, but you can find it on alternative download repositories such as this one: https://download.cnet.com/Image-Comp...-75207152.html. Could be an option to try.

[Dave882 (David)]

Another vote for APP. Very easy to do.
They have a free / unrestricted trial if you wanted to test it out

[SB (Chris)]

Hi Steve.
What overlap % did you use for the frames? I have had good success with Affinity with the panorama stitching. I do remember one time where I had trouble and it was because I needed a larger overlap. I’m using 15% overlapping currently but it does depend on the target as there needs to be enough points for the stitch to compute. Having said that one would have thought Carina would provide plenty of points for the stitching process.

Chris

[Nikolas (Nik)]

This is still incomplete, I have added another panel since this was taken and more panels to come but not till next season now.
In astropixel processor I stacked each panel separately then the final stacked panels were "restacked" in a sense as a mosaic, make sure that all are cropped when doing so and there is plenty of overlap. I still have a way to go but it's coming along.
Astropixel processor is a very good tool for mosaics LNC and multi band blending allow for seamless integration, When I get all the panels together I will be processing further as this image is just a simple stretch currently

[AstroViking (Steve)]

Hey all,

Thanks for the pointers to APP. I grabbed their 30-day free trial and spent last night learning the (very) basics of how to drive it.

Somehow I managed to get a very clean mosaic out the end of the process. I want to go back and do it all again because I missed a setting to do with light pollution removal when I was stacking each of the 4 panels. Oops...

Chris/SB - I specified a 10% overlap when setting up the mosaic panels in the Ekos 'Mosaic Creator' tool.

I think the problem came from the stacking artifacts in SiriL - there were horrible lines and purple streaks along the edges of the panels that looked to be as wide as (or wider) than the 10% margin and they confused Affinity's panorama tool.

Stacking the same subs in APP with MBB and NLC enabled gave me clean panels with no garbage on the edges - and much better colour / detail overall. The mosaic came out with no visible seams and a balanced colour palette across the entire image.

Nik - WOW! That's a total ripper of an image. I can't wait to see what the final product looks like.

Now I know what APP can do, I will go back and reprocess old image data with it and see what comes out. Expect a flood of images over in the image section...

Thanks again for the pointers.

Cheers,
V

[SB (Chris)]

Hi Steve,
Last night I tried out the Mosaic Plan in ASIAIR and used the Panorama function in Affinity Photo. I used 15% overlap.

I set up 8 regions in the plan and exposed each region for 30 minutes (10X180 sec) Ha for each frame. Esprit 100, Antlia 3.5nm Ha, ASI 183MM. One meridian flip.

Here is the result.

Chris

[bojan]

Have you tried Registar (Auriga Imaging)?

[AstroViking (Steve)]

Hey Chris,

Great looking image of EtaCar. Although I'm not sure about the colour...

Did you stitch the mosaic together before or after you stretched the data? I just read (today, in fact) that you should stitch the panels together before doing any stretching. Which makes sense when you think about it, as each panel may have different stretching.

Originally Posted by bojan

Have you tried Registar (Auriga Imaging)?

That's one thing I forgot to mention in my original post - my processing machine runs MacOS, not Windows.

Cheers,
V

[Drac0 (Mark)]

Maybe take a look at ASTAP - free & available for the Mac.

I'm using it for most of my stacking now, but it also has a number of other useful functions such as plate solving (compatible with a number of imaging programs), deep sky and star annotation, pixel math & CCD inspector for things like measuring camera tilt. Once you work out the mosaic stacking it seems to go quite well on the few chances I've had to try it (damn weather). Just another option to consider.

Cheers,
Mark

[SB (Chris)]

Attachment 304592

Originally Posted by AstroViking

Hey Chris,

Great looking image of EtaCar. Although I'm not sure about the colour...

Did you stitch the mosaic together before or after you stretched the data? I just read (today, in fact) that you should stitch the panels together before doing any stretching. Which makes sense when you think about it, as each panel may have different stretching.


That's one thing I forgot to mention in my original post - my processing machine runs MacOS, not Windows.

Cheers,
V

Hi Steve,
Interesting post. I have wondered about stitching before stretching or stretching before stitching so I did a comparison. When I stitched prior to stretching Affinity couldn't combine two of the panels ( as these were the ones with less detail perhaps). I think the 'stitching before stretching' may have the edge.

Chris.