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Thanks, David! The video is still private.
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Sorry,… my first video. Should be good now. Dave |
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11.24
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Sorry,… my first video. Should be good now. Dave |
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Very nice tutorial, clarifies the meaning of the individual parameters a lot. Thanks a lot Wolfgang |
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@David Payne Thank you for your work on this and sharing it - great to see that a script was cranked out, too (Thanks Mike!). I've played around with it a little bit so far, and I am really liking the control on has without relying on being super careful with a mouse in drawing curves, etc. Great stuff!!
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Finally managed to use your script on a larger data set - although not my own. I'm quite happy with the result: Centaurus A ( kuechlew ) - AstroBin All flaws of the image are mine ... Best regards Wolfgang |
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Finally managed to use your script on a larger data set - although not my own. I'm quite happy with the result: Centaurus A ( kuechlew ) - AstroBin Nice work Wolfgang. Thanks for sharing this. All the best Mike |
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Thank you. I will try. I think the parametric form are useful, even when sometimes they need more time. |
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There is an excellent presentation on GHS, what is behind it and how to use it by Mike and David on the Astro Imaging Channel https://www.youtube.com/watch?v=-DTmKTnEhvM exquisite job, thank you - well worth to get up early! |
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Thanks for the compliment. It was a lot fun to do. Dave |
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I watched a few videos. It seems like a very nice addition to PI. Thanks for all your effort!
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There is an excellent presentation on GHS, what is behind it and how to use it by Mike and David on the Astro Imaging Channel Thanks GalacticRAVE, I am glad you felt it was worth the early start! CS Mike |
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Alan: Thanks for the feedback Alan, I hope you will find it useful. CS Mike |
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David, thank you for sharing this. Based on your and Mike Cranfield's work I've written equivalent code to implement this for Siril too, so that the technique is available for users of that processing software as well as PI. No fancy GUI just yet but at least the stretches are there, and adding the histogram GUI and MTF display to the Siril code is next on my list.
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Adrian Knagg-Baugh: That sounds great Adrian, I am sure there are many Siril users out there who will welcome your efforts. Let me know if you need any help. Where are you making it available for download? |
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Based on my experience working with 2 planetary nebulae the GHS proved to be invaluable in being able to both show the extremely bright central detail and the faint outer envelopes. It's an essential tool for me right now.
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Mike Cranfield:Adrian Knagg-Baugh: Thanks Mike. I've submitted a merge request to the Siril team for inclusion in a future release but currently it's available at https://gitlab.com/aje.baugh/siril. |
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Thanks Adrian, A buddy in my club was just on to me about contacting the Siril developers about Adrian Knagg-Baugh: Thanks Adrian, A buddy in my club was just on to me about contacting the Siril developers about suggesting the concept to you. He is very much in the Siril + GIMP camp for the bulk of his image processing. What I like is that it is open source and free - just as the GHS script for Pixinsight is. Is it an add-on or is it contained in a release? I would like to give it a spin (as well as Siril itself - my buddy swears by it). As Mike suggested, we are both available to help - Mike more with the interface - (I am particularly adept at Fortran 77 & Excel/VBA but I doubt this is what you are looking for). I look forward to using it. Dave |
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11.24
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Based on my experience working with 2 planetary nebulae the GHS proved to be invaluable in being able to both show the extremely bright central detail and the faint outer envelopes. It's an essential tool for me right now. Thanks trans-at, I'm glad you are finding it useful - what you describe is the result we were after. |
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David Payne: Thanks Dave. I've submitted a merge request to the main repository, which hopefully Vincent will approve sooner or later, but for now you can find my version at my gitlab fork here, if you want to give it a try. (If you're willing, I'd be grateful for confirmation that for the same parameters it does actually produce the same result as the PI code. At the moment I don't have decent source data on a planetary nebula or similar high dynamic range object, so I've tried it on an image of Abell 2151 that I took a couple of months back but that doesn't really exercise the shadow and highlight preservation as well as the planetary nebula images posted further up this thread. My next step is improving the UI, at the moment it's just a few sliders that affect the preview, but the next version will have a UI that mirrors siril's histogram stretch window and shows the histogram and MTF. Hopefully it shouldn't be too hard as I'm aiming to reuse as much of their existing code as possible, I'm just at the stage of copying all the functions, changing object names to avoid clashes, (generally cursing the glade user interface design tool!) and trying to get a duplicate histogram window working and then I'll add the guts of my first siril version so as to get a nice preview of the effect on the histogram and the transfer curve. But I'm grateful for the offer of help and if I get stuck I might send a question or two to you or Mike  |
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@Adrian Knagg-Baugh@David Payne@Mike Cranfield : I sent you a private astrobin message about Siril testing ;). Cheers, Cyril |
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maybe I have missed it in previous posts - but when I use this on my images - I feel like the background noise (space background) is much less compared to traditional stretch techniques (I don't think this is described as big of a feature of the stretching approach as some of the other components). I am using noise suppression (NoiseExterminator) but to do similar stretching with things like this histogram transformation tool - the background seems to have a lot of noise. When I use the GHS script with your SP settings like you showed on the AIC demo - it comes out so clean! Great work - after I learned to use it and tried the same image with histogram transformation - The results we vastly different. GHS is my new go to! |
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Brent: Hi Brent, You are correct that I haven't really discussed this much and I agree that you can also control the background noise. Without the ability to move the greatest contrast add off of the zero or black-point, that is where the maximum contrast is placed with HT. The thought is that by moving SP above the background noise, to the point where you also have signal and putting a lot of contrast right there, you separate in brightness, or provide contrast between the background noise and that signal. In practice it is not a line though, just a gradual SNR that emerges from the background noise - the dimmer/weaker the signal you go after, the more noise you are going to get unless you add more integration time. I too have recently acquired and used NoiseExterminator (although the unually poor weather here has reduced our recent clear sky time to absolute 0). I find it fantastic, although I think the denoise slider default setting of 0.9 is far too high. I'm super glad you are enjoying the script, it is really motivating to Mike and I. I'm super excited to see it in Siril as well! CS! Dave |
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Hello @David Payne and fellow astronomers, thanks a lot for sharing your formulas and your analysis and graphs about the generalized hyperbolic stretch transformations. This is very helpful for our whole community. Thank you for taking the time ! As a Siril user I often perceive that general concepts of astroprocessing are described with the perspective of a PixInsight user - which is absolutely OK. Beginners may conclude then that the features are only available in PI, or even are inventions of the PI programmers. This is neither the case for the GHS algorithms nor (for example) for star extraction with StarNet and other functions. Stumbling over this thread after I have used GHS in Siril, I just would like to say that the GHS algorithm is also included in Siril with a very convenient GUI. A highly recommended and valuable addition to the toolbox Regards, Goetz |
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Götz Golla: Hi Goetz, I agree with you, but ultimately it takes a programmer to actually put the algorithm/method into code and create a GUI for it. Thanks to @Mike Cranfield and @Adrian Knagg-Baugh for doing this for Pixinsight and Siril respectively - they are even collaborating on both. I am glad you like the process/script. Cheers, Dave |
