Back to forums

Gradient Merge Mosaic Not Properly Merging Images

Unspecified/unknown company PixInsight Mosaic by Coordinates Mosaic Processing
10 replies•297 views
Derek Vasselin avatar
Derek Vasselin avatar
I've been trying to do a 2-panel mosaic. Below is the result I get from GradientMergeMosaic. 

As you can see from the 2 images below, it's not correctly combining them. The top image is super blurry and the bottom image is super grainy and the contrast is screwed up.

My steps to this point:
- Did a STF
- Resampled at 50%
- Cropped
- DBE
- Image solver to plate solve
- Mosaic by coordinates (see settings below)
- Gradient merge mosaic (see settings below)

I've played around a bit with these settings, but nothing has fixed it.

Any ideas what's going on? Am I missing something?

I have successfully done this before with the same process, so idk why this time is different.

Thanks in advance!
Well Written Engaging
Brian Puhl avatar
Brian Puhl avatar
See if you can get ahold of PMM or PhotographicMergeMosaic.   It's been discontinued but it's much better at doing mosaics.   I've not seen very good results from GMM.   I think with some Google you can find the script online.  I keep it saved in my files in case I update pix.
Shun-Chia yang avatar
Shun-Chia yang avatar
That is because these two images have different brightness levels. You can use linearfit to make both images have the same brightness. Be cautious; it needs to be done before mosaic alignment.
Wei-Hao Wang avatar
Wei-Hao Wang avatar
Brian Puhl:
See if you can get ahold of PMM or PhotographicMergeMosaic.   It's been discontinued but it's much better at doing mosaics.   I've not seen very good results from GMM.   I think with some Google you can find the script online.  I keep it saved in my files in case I update pix.

Are you talking about the photometric mosaic script?  It's very powerful and it's not discontinued.  It's just no longer included in the standard PI installation.  You can install it by yourself.  It can be found here:
https://www.astroprocessing.com
Well Written Helpful Concise
Andre Vilhena avatar
Andre Vilhena avatar
Tipically GMM works best with stretched imagens - try to stretch both and then run the process. If it doesn't work, then I would go for PMM, as other colleagues are mentioning.
​​​
Bob Lockwood avatar
Bob Lockwood avatar
You have PS, have you tried there Photomerge, I've used it, works quite well.
Tony Gondola avatar
Tony Gondola avatar
The mosaic function in Affinity Photo works nicely as well.
Well Written
Derek Vasselin avatar
Derek Vasselin avatar
Shun-Chia yang:
That is because these two images have different brightness levels. You can use linearfit to make both images have the same brightness. Be cautious; it needs to be done before mosaic alignment.

This worked, thank you!

Only note was I had to use DNA Linear Fit instead because regular linear fit gave me errors.

Only other downstream issue was the bright stars where the image overlapped was giving me some strange artifacts. But I was able to solve that with pixel math (following the pinched star technique here: http://trappedphotons.com/blog/?p=994).

Aside from that, just needed to hit the image with a quick background neutralization afterwards to equalize the green tint.

Helpful Concise
Derek Vasselin avatar
Derek Vasselin avatar
Wei-Hao Wang:
Brian Puhl:
See if you can get ahold of PMM or PhotographicMergeMosaic.   It's been discontinued but it's much better at doing mosaics.   I've not seen very good results from GMM.   I think with some Google you can find the script online.  I keep it saved in my files in case I update pix.

Are you talking about the photometric mosaic script?  It's very powerful and it's not discontinued.  It's just no longer included in the standard PI installation.  You can install it by yourself.  It can be found here:
https://www.astroprocessing.com

The website doesn't seem to be functioning right now. Anyone know what's going on there?
Well Written Respectful
Wei-Hao Wang avatar
Wei-Hao Wang avatar
Derek Vasselin:
Wei-Hao Wang:
Brian Puhl:
See if you can get ahold of PMM or PhotographicMergeMosaic.   It's been discontinued but it's much better at doing mosaics.   I've not seen very good results from GMM.   I think with some Google you can find the script online.  I keep it saved in my files in case I update pix.

Are you talking about the photometric mosaic script?  It's very powerful and it's not discontinued.  It's just no longer included in the standard PI installation.  You can install it by yourself.  It can be found here:
https://www.astroprocessing.com

The website doesn't seem to be functioning right now. Anyone know what's going on there?

No problem here.
Derek Vasselin avatar
Derek Vasselin avatar
Wei-Hao Wang:
Derek Vasselin:
Wei-Hao Wang:
Brian Puhl:
See if you can get ahold of PMM or PhotographicMergeMosaic.   It's been discontinued but it's much better at doing mosaics.   I've not seen very good results from GMM.   I think with some Google you can find the script online.  I keep it saved in my files in case I update pix.

Are you talking about the photometric mosaic script?  It's very powerful and it's not discontinued.  It's just no longer included in the standard PI installation.  You can install it by yourself.  It can be found here:
https://www.astroprocessing.com

The website doesn't seem to be functioning right now. Anyone know what's going on there?

No problem here.

Works now for me as well. Must have been down for maintenance at the time.
Well Written