Help need with Stitching a Mosaic together?

[AstroKriss]

Hi all, I recently attempted my first 4 panel mosaic image capture through my ASIAir. I have I have stacked all the images from each panel, and cropped out Dithering artifacts so I now have 4 stacked FITS files. But for the life of my I have no idea how to merge the Fits together into a single larger FIT files. Can anyone share some experience on how to this on macOS software? 

I know I could just convert them into TIFF or something and try to manually stitch them in PhotosShop, but was hoping to find a way to stitch the Stacked FITs files together before processing them all as one single image. 

Any tips or advice? I currently stack and process my images in SiriL. 

Thanks

[Paul M]

I've used ASTAP for mosaic stitching. It worked very well although my individual panels had such strong gradients the final image was a bit pants!

Here is a post I made midway through a topic I'd started.

 

The ASTAP user guide gives details. It's just a case of making sure the right settings have been selected.

Stack method tab, Image stiching method (Mosaic)

Astrometric image stiching is possible with the internal astrometric solver. The reference of each pixel is the astronomical position. So stacking is not done against a reference image but against an position array set by the first image.  You have to set the in tab alignment the settings for "Image stiching (method)" correctly. If you stitch 4 images, you have set "Mosaic width/height  in tiles:" at 2. This will provide enough space to place for the 2x2 mosaic.

Here a suggested work method:

1. Stack the tiles separately using method "SIGMA-CLIP-average" and use for the alignment the internal STAR alignment method.  Inspect the resulting tiles and crop them if required. You can also crop them later automatically with "Mosaic skip outside pixels" Do this for each color separately if you have separate files.
2. In tab  "stack method" select option "IMAGE STICHING METHOD" and select astrometic alignment using either the internal solver.
3. In tab "stack method", set the "mosaic width/height" correct and check-mark the option "equalise background".  If the input images have poor borders, set option crop images larger then 0%.
4. Select the files. Most likely the files names contain "_stacked, so you have the check-mark the files after selection.
5. Click on the button   Stack check marked images|  
6. Crop the stacked result using the image crop option in the viewer mouse pop-up menu.
7. Adjusted the stretch range and save as JPEG, 90% quality.

Here an example mosaic x 4 of M31 made with ASTAP:

http://www.hnsky.org/astap_mosaic%20x%204.jpg



Here an example of a mosaic build of DSS images:
http://www.hnsky.org/astap_mosaic.png
The size can be reduced by a crop function (right mouse button) later. Making the oversize too large could result in memory overload.



If you have  DSLR/OSC sensor and using a monochrome filter like H-alpha, you can split the raw the images in seperate R, G, G, B  image using the viewer Tools, Batch processing, Raw colour seperation menu. In case of H-alpha use only the R=red image for future processing.

[Chris-h]

Microsoft ICE is now discontinued, but it can still be found on the net. It is free and works well on auto settings 98% of the time.

It does not take .fit files though

Edited September 8, 2023 by Chris-h

[AstroKriss]

3 hours ago, Paul M said:

I've used ASTAP for mosaic stitching. It worked very well although my individual panels had such strong gradients the final image was a bit pants!

Here is a post I made midway through a topic I'd started.

 

The ASTAP user guide gives details. It's just a case of making sure the right settings have been selected.

Stack method tab, Image stiching method (Mosaic)

Astrometric image stiching is possible with the internal astrometric solver. The reference of each pixel is the astronomical position. So stacking is not done against a reference image but against an position array set by the first image.  You have to set the in tab alignment the settings for "Image stiching (method)" correctly. If you stitch 4 images, you have set "Mosaic width/height  in tiles:" at 2. This will provide enough space to place for the 2x2 mosaic.

Here a suggested work method:

1. Stack the tiles separately using method "SIGMA-CLIP-average" and use for the alignment the internal STAR alignment method.  Inspect the resulting tiles and crop them if required. You can also crop them later automatically with "Mosaic skip outside pixels" Do this for each color separately if you have separate files.
2. In tab  "stack method" select option "IMAGE STICHING METHOD" and select astrometic alignment using either the internal solver.
3. In tab "stack method", set the "mosaic width/height" correct and check-mark the option "equalise background".  If the input images have poor borders, set option crop images larger then 0%.
4. Select the files. Most likely the files names contain "_stacked, so you have the check-mark the files after selection.
5. Click on the button   Stack check marked images|  
6. Crop the stacked result using the image crop option in the viewer mouse pop-up menu.
7. Adjusted the stretch range and save as JPEG, 90% quality.

Here an example mosaic x 4 of M31 made with ASTAP:

http://www.hnsky.org/astap_mosaic x 4.jpg



Here an example of a mosaic build of DSS images:
http://www.hnsky.org/astap_mosaic.png
The size can be reduced by a crop function (right mouse button) later. Making the oversize too large could result in memory overload.



If you have  DSLR/OSC sensor and using a monochrome filter like H-alpha, you can split the raw the images in seperate R, G, G, B  image using the viewer Tools, Batch processing, Raw colour seperation menu. In case of H-alpha use only the R=red image for future processing.

Awesome thanks, will have a go at this  

[Paul M]

39 minutes ago, AstroKriss said:

Awesome thanks, will have a go at this  

If you hit any snags just post here,  I might be able to help.

I found building a mosaic to be very satisfying. I know, I could have done a much better job of the pleiades by using a suitable instrument but where is the fun in trudging down a well trodden path?😁

And the clouds and light summer nights don't stop us playing with software.

[Elp]

4 hours ago, Chris-h said:

Microsoft ICE is now discontinued, but it can still be found on the net. It is free and works well on auto settings 98% of the time.

It does not take .fit files though

I'd err some caution with this. By all means try and stitch but also compare the stitch to a reference image. My last 9 panel, 3 x 3, even trying horizontal 1 x 3 at a time didn't stitch, the integration looked okay, but when I compared to my manual PS overlay the galaxies were in different positions with some even missing.

[ONIKKINEN]

Probably not the answer you were hoping for, but paid software make short work of mosaicing (and are the least headache inducing).

Astropixelprocessor works well for most simple mosaics, and the Photometric mosaic script in PixInsight will surely mosaic any panels together if they can be. Astropixelprocessor can be rented for i believe 60€/year or something like that last i checked, and they have a free trial too. PixInsight costs 250€+tax, but they also offer a free trial on request.

The tool in PixInsight is more complicated to run and requires you to read the instructions thoroughly. Astropixelprocessor mosaicing is a lot easier in that you first just stack the panels individually and then re-run integration with the panels in mosaicing mode.

[Paul M]

18 minutes ago, ONIKKINEN said:

Astropixelprocessor mosaicing is a lot easier in that you first just stack the panels individually and then re-run integration with the panels in mosaicing mode.

That's pretty much how ASTAP does it too, for free!!

[tomato]

APP (and PI) do some clever gradient smoothing between the panels to manage the joins between them if taken under different sky conditions, does ASTAP do something similar?

[ONIKKINEN]

26 minutes ago, Paul M said:

That's pretty much how ASTAP does it too, for free!!

Was not aware that ASTAP had this option. Have to try it now for sure!

[Paul M]

40 minutes ago, tomato said:

APP (and PI) do some clever gradient smoothing between the panels to manage the joins between them if taken under different sky conditions, does ASTAP do something similar?

It does indeed, but my gradients beat it!

Even Han, the developer of ASTAP, couldn't fix my gradients. But that's Blackpool Illuminations for ya!

[John_D]

I've had some success with daytime landscape panoramas using Hugin ( FOSS ) on Linux but I don't know how well it would work here. There is a Mac version but you would have to convert your files to TIFF.

[AstroKriss]

9 hours ago, John_D said:

I've had some success with daytime landscape panoramas using Hugin ( FOSS ) on Linux but I don't know how well it would work here. There is a Mac version but you would have to convert your files to TIFF.

Hi John, yeah I found that yesterday too, seems to be a good option although had to covert to JPEGs first but seemed like I got a good result from it: 

https://astrokriss.com/my-photos/galaxies/

The top image of m31 is the result which I’m quite pleased with.

[John_D]

14 hours ago, AstroKriss said:

Hi John, yeah I found that yesterday too, seems to be a good option although had to covert to JPEGs first but seemed like I got a good result from it: 

https://astrokriss.com/my-photos/galaxies/

The top image of m31 is the result which I’m quite pleased with.

That looks great to me, it seems to have merged seamlessly. Did you need to be careful with the initial processing of the 4 images to get the merge to work?

( I thought Hugin would work with TIFFs but then again I've only ever used JPGs )

[WolfieGlos]

On 08/09/2023 at 23:36, Paul M said:

It does indeed, but my gradients beat it!

Even Han, the developer of ASTAP, couldn't fix my gradients. But that's Blackpool Illuminations for ya!

I didn’t realise it did this, but that’s good to know.

I’ve used ASTAP successfully for 2 mosaics now, albeit they were only 2x1, and it was really straightforward. 

[AstroKriss]

On 08/09/2023 at 22:41, Paul M said:

That's pretty much how ASTAP does it too, for free!!

Hi Paul, do you have link or details on steps to do this in ASTAP? Would like to try it, but not clear on how to. Thanks 

[AstroKriss]

1 hour ago, John_D said:

That looks great to me, it seems to have merged seamlessly. Did you need to be careful with the initial processing of the 4 images to get the merge to work?

( I thought Hugin would work with TIFFs but then again I've only ever used JPGs )

So I fir this one stacked the lights from each panel in SiriL, opened the stacked fit file, cropped out the edges dithering, then only performed histogram and asinh transformations. Save the resultin fit file and as a jpg. Then just used the jogs to stitch together with Hugin. 
 

overall not too difficulty a process. 

[Paul M]

9 hours ago, AstroKriss said:

Hi Paul, do you have link or details on steps to do this in ASTAP? Would like to try it, but not clear on how to. Thanks 

It's a while since I used it but here is the method given in the ASTAP user guide:http://www.hnsky.org/astap.htm

So, I'll do it again with the original stacked frames linked in my first post in this thread. See how I do!

Here are my 6 stacked frames (all calibration done in the stacking of each frame, don't apply flats, darks etc for this stage). Just load them in the "lights" tab and make sure they are all selected. Click analyse and it should look something like this:

In the "Alignment" tab select "Astrometric Alignment". Most of the other settings on that page are defaults for what we are doing now, but can look intimidating.   

In the Stack Method" tab select "Image Stitching Mode", and here I've opted to Equalise Background, Merge Overlapping Backgrounds. My mosaic is 2 rows high (the latest version of ASTAP does that automatically but I've had trouble with that development version just now), The 6% auto crop is just a number I liked the look of...

 

Then select "Stack (image stitching mode)" 

After a while my modest lappy gave this:

Which can be cropped by Right Clicking at one corner of the image and dragging out a crop box. 

Select Crop and hey presto, I have a whole world of gradients.

The gradients are my problem not ASTAPS.

The very latest version has a box to reduce overcorrection of gradients. But as above, that version wouldn't produce a mosaic on this occasion. 

Good Luck.

[AstroKriss]

7 minutes ago, Paul M said:

It's a while since I used it but here is the method given in the ASTAP user guide:http://www.hnsky.org/astap.htm

So, I'll do it again with the original stacked frames linked in my first post in this thread. See how I do!

Here are my 6 stacked frames (all calibration done in the stacking of each frame, don't apply flats, darks etc for this stage). Just load them in the "lights" tab and make sure they are all selected. Click analyse and it should look something like this:

In the "Alignment" tab select "Astrometric Alignment". Most of the other settings on that page are defaults for what we are doing now, but can look intimidating.   

In the Stack Method" tab select "Image Stitching Mode", and here I've opted to Equalise Background, Merge Overlapping Backgrounds. My mosaic is 2 rows high (the latest version of ASTAP does that automatically but I've had trouble with that development version just now), The 6% auto crop is just a number I liked the look of...

 

Then select "Stack (image stitching mode)" 

After a while my modest lappy gave this:

Which can be cropped by Right Clicking at one corner of the image and dragging out a crop box. 

Select Crop and hey presto, I have a whole world of gradients.

The gradients are my problem not ASTAPS.

The very latest version has a box to reduce overcorrection of gradients. But as above, that version wouldn't produce a mosaic on this occasion. 

Good Luck.

This is awesome, thanks sharing, I’ll be sure to give this a go  

[Paul M]

I've been playing with the latest ASTAP version again. I've got it going after selecting "ignore existing FITS header solution for astrometric stacking" in "Alignment" Tab.

This version auto arranges the frames without specifying how many rows it contains.