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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

measure of the background

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Madhav, thank you for your work on this new Stats tool. I've already found it useful. I would like to see min and max included. Thank you.
1 year 7 months ago #84854

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Replied by MORELLI on topic measure of the background

Did the SHIFT and mouse drag is operating ? Not in my case.
1 year 7 months ago #84858

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I read it in the announcement, and immediately checked it out. Works perfect here, and really makes usage a lot easier!
1 year 7 months ago #84860

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Replied by MORELLI on topic measure of the background

In fact, the SHIFT and mouse drag operates once you have choosen an existing probe. You can't use directly.
1 year 7 months ago #84869

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You don't have to select a probe. It is enough to just click the button/icon to activate the module. If it isn't active, the shortcut of course won't work...
1 year 7 months ago #84888

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Replied by MORELLI on topic measure of the background

OK.
1 year 7 months ago #84892

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Replied by MORELLI on topic measure of the background

Hello,

after using this new feature, some remarks:

- the way the square must be set on the image is not very convenient. It's best to draw the frame on the image at the desired location and size. As all the other software do: Pix, Siril, Iris
- the results of statistic, particulary sigma, of the frame is very different from the three others software: Iris, Pix, Siril as you can see on the joined images. Why ?

Thank for your answer.
Last edit: 7 months 4 days ago by MORELLI.
7 months 4 days ago #95115
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>> the results of statistic, particulary sigma, of the frame is very different from the three others software: Iris, Pix, Siril as you can see on the joined images. Why ?

I just took a glance in the statistics functions of siril and kstars. The algorithms used seem a bit different to me, however I think using functions like sqrt(), division etc.. are bound to cause inaccuracies with floating point numbers.

This link gives an insight about what those inaccuracies could be. So this inaccuracy in each stage of computation may or may not get exaggerated, and this exaggeration will be different for different algorithms. Sometimes choosing to do some mathematical operations before or after a stage in the same algorithm may work out on paper but not on computers.

I'd love Jasem's take on this too.

>> - the way the square must be set on the image is not very convenient. It's best to draw the frame on the image at the desired location and size. As all the other software do: Pix, Siril, Iris

Drawing the frame is possible with shift+click if thats what you are looking for. However if you want to specify x,y and size for the square thats a new thing
7 months 2 days ago #95217

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Replied by MORELLI on topic measure of the background

Thanks for your answer.I am not a programmer so the link you gave was not very accurate for me. I understand it may be some problems with the calculation. Are we standing an answer from Jasem ?
Best regards
Last edit: 7 months 2 days ago by MORELLI.
7 months 2 days ago #95223

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Okay, so thing with computers is that they can only store numbers up to a certain precision. For example the number 0.3 is probably stored as 0.30000000000000004. So when we do operations, this outcome will be different than what is expected. This also paves a way for rounding errors, division errors, error over errors as we stack up operations.

Ideally, we should use scientific computing libraries to solve this issue but that would slow down computations and will require a lot of change in the codebase. This is probably not feasible for the gain in accuracy and is probably the reason why both kstars and siril doesn't use those libraries.

Thanks and Regards
7 months 1 day ago #95235

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Replied by nou on topic measure of the background

Main source of floating point inaccuracies comes when you do operation on numbers with vastly different magnitudes. For example if you try +1 to 20million you will end up with 20 000 002 because float can't represent 20 000 001.
But this errors pops up when you try calculate stddev from millions of pixels. 100x100 pixels should be just fine even with float.
7 months 11 hours ago #95260

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Replied by MORELLI on topic measure of the background

I am OK with the calculation difficulties but the size of the frame, even designed by me. It is little less than 100x100.
7 months 11 hours ago #95261

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