Pixinsight image stretching – GHS Version 2 Pleiades Astrophoto PixInsight · Mike Cranfield · ... · 376 · 35404 · 289

In December 2021, I issued version 1 of the Generalsied Hyperbolic Stretch (GHS) script for Pixinsight.  Since then many Pixinsight users have incorporated GHS into their workflow to great effect (including competition winning images!) The script provides a complete integrated environment to define, analyse and apply stretches within Pixinsight.  It incorporates the GHS equations which allow a high degree of control over your image stretches, adding contrast exactly where you want it, preventing bloated stars, and controlling background noise.  

Here are just a few comments from GHS users:

• “incredible breakthrough improvement to linear stretching in PixInsight”
• “This script will remain a permanent part of my workflow, it's really fantastic”
• “it’s become my first port of call for the stretch”
• “really makes it feel like you are in control of what happens to the image”
• “I can't say enough good things about how Mike's script created a superb framework for stretching images and removed most of the guesswork from this part of the processing”

I am now really pleased to make version 2 of GHS available.  The key improvements from version 1 include the following:

• Real-time preview
• Luminance, saturation and colour stretches
• Full masking support
• Additional stretch types
• Secure repository updates (much easier to install!)
• Dedicated website (https://ghsastro.co.uk) with tutorial videos and more – available directly from within the script

If you are a Pixinsight user and haven’t yet tried GHS, I would really encourage you to give it a go – it’s free!  If you are already a GHS user, thank you for your support and to many of you, thanks also for your feedback and suggestions.  Many of your suggestions have helped inform the content of this release – please do keep them coming! 

To install GHS into Pixinsight, add the repository information as follows:

• If you have GHS Version 1 installed then remove this first, then ...
• From within Pixinsight go to: Resources>Updates>Manage Repositories
• In the Manage Update Repositories dialog, click the Add button
• In the URL box type the GHS repository information as follows: https://www.ghsastro.co.uk/updates/
• In the Add Pixinsight Repository dialog, click the OK button
• In the Manage Update Repositories dialog, click the OK button

When you next sign back into Pixinsight you will receive a message to say there are updates available which will include GHS.  Proceed in the same way as you would for any Pixinsight update (including restarting Pixinsight) to complete the installation. 

Your comments, feedback and suggestions are very welcome. 

Happy stretching and clear skies! 

Mike Cranfield

Michael Ring:
Autoupdates via pixinsight, a great tool has gotten even better, many thanks!

Thanks Michael - I am happy you find GHS useful.

I’ll download and give it a try.

Thanks Mike!

Dale

Dale Penkala:
I’ll download and give it a try.

Thanks Mike!

Dale

Thanks Dale, I hope you find it helpful.

Fantastic - this has made a great tool much more easily useable

Installed and been playing with this. Very impressed with the Arcsinhstretch-like color (using “col”) without the artifacts. And the ability to blend with other stretches directly in the script with preview is also very powerful. So far so good. Nicely done!

Mike, sorry, I tried to install the new version of GHS but in PI, under Script, Utilities, I see only the old version (v1).
Is it mandatory to uninstall the previous version before installing the new version?
Could be this the issue?
Thanks in advance.
Ciao
Lorenzo.

Michael Timm:

Lorenzo Siciliano:
Is it mandatory to uninstall the previous version before installing the new version?

Hi Lorenzo,

you need to delete the old version, it is mandatory.
Thanks guys for this really helpful script, the new version is incredible :-)

CS
Michael

Actually I managed to keep both by having them in folders with different name (in my case GHS_v1 for the first version). It comes at the price of having two entries with the same name in the dropdown menu. so you have to remember which is which. 


As soon as the much appreciated version 2 - a nice improvement on an already great product - turns out to be robust when I use it the next weeks, there is no more reason to keep the old one.

I really like the introduction videos. even using the script regularly over the last weeks I still got some additional ideas out of them.

Clear skies
Wolfgang

Michael Timm:

Lorenzo Siciliano:
Is it mandatory to uninstall the previous version before installing the new version?

Hi Lorenzo,

you need to delete the old version, it is mandatory.
Thanks guys for this really helpful script, the new version is incredible :-)

CS
Michael

Actually I managed to keep both by having them in folders with different name (in my case GHS_v1 for the first version). It comes at the price of having two entries with the same name in the dropdown menu. so you have to remember which is which. 


As soon as the much appreciated version 2 - a nice improvement on an already great product - turns out to be robust when I use it the next weeks, there is no more reason to keep the old one.

I really like the introduction videos. even using the script regularly over the last weeks I still got some additional ideas out of them.

Clear skies
Wolfgang

Hi Wolfgang.
How did you do that?
For what I know, the automated update doesn't give any folder choice...

Just saw this post on the front page and tried it for the first time. To be honest I don't particularly like to strongly disrupt the light/dark relationship, so I got similar results with it to PI's histogram stretching (though better). I think the one of the best things is that it prevents the dark areas from being stretched violently and amplifying the noise. It gets the dark areas are very clean! Excellent script!

Lorenzo Siciliano:

Michael Timm:

Lorenzo Siciliano:
Is it mandatory to uninstall the previous version before installing the new version?

Hi Lorenzo,

you need to delete the old version, it is mandatory.
Thanks guys for this really helpful script, the new version is incredible :-)

CS
Michael

Actually I managed to keep both by having them in folders with different name (in my case GHS_v1 for the first version). It comes at the price of having two entries with the same name in the dropdown menu. so you have to remember which is which. 


As soon as the much appreciated version 2 - a nice improvement on an already great product - turns out to be robust when I use it the next weeks, there is no more reason to keep the old one.

I really like the introduction videos. even using the script regularly over the last weeks I still got some additional ideas out of them.

Clear skies
Wolfgang

Hi Wolfgang.
How did you do that?
For what I know, the automated update doesn't give any folder choice...

Hi Lorenzo,

you can't influence the folder name of the upgrade indeed but you can rename the folder of Version 1 instead of deleting it.

You find the folder in PixInsight/src/scripts. Rename it to your liking. Then you can add it in PixInsight via SCRIPT>Feature Scripts...
Just click on "Add" and point to your folder.

I actually discovered this by accident because my initial installation was already in a folder GHS_v1. So the automatic upgrade just created the second entry.

Hope this helps
Wolfgang

That did the trick! 
Thank you so much, Wolfgang.
Ciao.
Lorenzo

Definitely giving it a go!

Mike - thank you very much for your efforts in creating this versatile script.  I have downloaded ver2 this week and following your tutorial I have processed a couple LRGB images and I have been impressed with my results on quite faint tricky targets.

If it's of any interest for performance, I have in the last couple of weeks bought a new Apple 14" MacBook Pro using the M1 Pro chip and GHS works very well.

I am not sure if I have spotted an issue though, after using GHS I had an error message regarding a 'preview' when I was using the Colour Mask script.  When I do not use GHS I do not receive the 'error' message.  I will note more detail if I get a chance tomorrow to process data and will update this thread.  The error message reported by PI did not appear to affect the performance of any process or script.  So it may be trivial if there is indeed some sort of issue.

Regardless of the above, the GHS script will be forming a routine part of my processing workflow.  Thanks once again.

Cheers, Barry