Generalised Hyperbolic Stretch - How I Find my Initial Stretch Parameters

[@starsips]

Great video Paulyman! I wasn't using the fine adjust of the SP *because I didn't fully understand it till now!* but more so, toggling both the stretch factor and local stretch intensity to yield impressed results! GHS is a power script! Another thing is that I've been removing my star in the linear state first before GHS and I've found this a nice process to preserve star size and brightness. It also means you can apply the GHS script to the stars prior to adding them back into the image with Pixelmath or processing them further. Thanks again mate! Your videos are great!

[@PaulymanAstro]

I’ve been doing similar with my stars. I do a mild stretch with GHS, remove them and then continue stretching and balancing colours. I’m finishing the final video on GHS where I’ve been playing with Eric Coles histogram balancing but using GHS.

[@starsips]

@@PaulymanAstro Awesome!! Looking forward to it 👍 We've been copping it bad weather-wise in Northern NSW. Wishing you clear skies!

[@johnparker9524]

Really appreciate your work on this and very much looking forward to the next video.

[@PaulymanAstro]

Thanks John.

[@MrSpike2450]

Brilliant as always and at a great pace. Looking forward to how you finish your work flow.

[@PaulymanAstro]

Thanks Spike.

[@starsips]

Been waiting for this video!! Cheers!!

[@IcedReaver]

Great video and well explained, thanks Paulyman! During my initial stretch I have not been setting the SP (I left it at 0) and just set the other two functions as you showed. I'm going to go back to my images and try this out :)

[@PaulymanAstro]

Thanks mate. I’m sure playing around with SP will produce some nice results.

[@thesummerhillstead2577]

This was incredibly helpful, thanks very much for your video!

[@PaulymanAstro]

Thank you, the latest version of GHS makes this process even easier thanks to the real time preview.

[@zakry3323]

@@PaulymanAstro The "copy to SP" button is a nice improvement too :)

[@paulyman1337]

@@zakry3323 very true.

[@gregorylatiak3333]

All nice, but what is the source for GHS and autocolour? I am current but am obviously missing script library references.

[@PaulymanAstro]

I go through how to install the script in my previous video, about 1 minute in kzbin.info/www/bejne/ip-8naiCgL2DnJo. But here is the direct link to the script: bit.ly/3L7ZPye. Here is a link to Herbert Walters page, he explains how add his repository to PixInsight. You will then not only have the autocolor script but many others such as psfimage and the awesome GAME script. www.skypixels.at/pixinsight_scripts.html

[@anata5127]

Is GHS more effective on starless images? So far, I could not manage GHS well, when stars are in picture.

[@PaulymanAstro]

It’s extremely effective at controlling stars, far more so than Histogram Transformation. A large initial local stretch intensity (b value), I start around 9 or 10 and if the stars are really close to saturated then maybe some highlight protection as well. But a starless workflow if possible is far easier to manage and means you can work on the nebulosity and stars independently.

[@anata5127]

@@PaulymanAstro I looked your 2023 version. There weren’t any stars. GHS window looks totally different from my. Then, I watched creators video. His window is exactly like my. His approach is very different from yours as well. I should admit, I don’t understand logic so far. It seems everyone use different approaches and change it all the time. For example, you have at least 4 versions. So, which one is best?

[@PaulymanAstro]

There is a script and a process for GHS. Many of my earlier videos were with the script, I now use the process. Stretching is more art than science, although GHS is the most scientific of them all. I don’t think there is one way that always works. As I continue to use GHS I’m constantly learning and so my workflow with it changes over time. David Payne has a much deeper understanding of the tool since he created it, his workflow with it is definitely one to look closely at, he does work more with RGB targets though. My workflow does revolve around working separately on the stars so you will almost always see me using GHS without stars, although I do use it to stretch the stars using high b value.

[@anata5127]

@@PaulymanAstro I watch video of Granfield (TAIC video). He had two picks. Initial stretch, then second stretch on another pick, which represents background. Your videos have one pick. Confusing, but I will get to a bottom of this. First symmetry point is near background. What is second and third stretches symmetry points? I use the script.