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

Bi-monthly release with minor bug fixes and improvements

New Bahtinov Mask Assistant Tool

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Perhaps you could compare it with whatver HFR value was showing just before the capture took place or take an average of the values (if its possible ofcourse) :-)
Another nice to have would be if there was some way to 'calibrate' it to understand if the focusser was moving in or out and then be more intelligent in suggesting what the user should do!
2 years 10 months ago #71647

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This is a very helpful thread about what must be a very helpful feature.
I am looking forward to using it as soon as I get a clear night.
2 years 2 weeks ago #81218

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Hi AstroRunner,
I have a question about the HFR when a Bahtinov mask is in place. Is that accurate or does the mask 'spoil' the view and HFR readings become less meaningful? i.e all that matters is how close is the centre line to the actual centre.
Last edit: 1 year 7 months ago by AstroMuni.
1 year 7 months ago #85222

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Hello Astromuni,
I am not sure to be the right person to answer. Otherwise, in my opinion, HFR with Bahtinov might be of poor help.
Maybe some people using this function can answer in a better way.
Clear skies
1 year 7 months ago #85223

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Didnt realise there were 2 Patricks in this conversation :-) I was hoping Astrorunner would respond.
1 year 7 months ago #85224

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The Bahtinov mask produces a strongly diffracted star image, for which something like a HFR doesn't make much sense. If you use such a mask for focus, look only at the position of the line. Reported HFR values are meaningless.

EDIT: This referred to HFR as what it actually means. I wasn't aware that the assistant calls the offset distance "HFR" - my bad :(
Last edit: 1 year 7 months ago by Peter Sütterlin.
1 year 7 months ago #85232

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Hi AstroMuni,

The HFR does not represent the same as with the other focus methods. But the HFR is not meaningless. The HFR in the Bahtinov mask focus assistant is a value that represents the offset to optimum focus. This means that the closer this value is to 0, the better you are in focus, where 0 represents perfect focus. Unfortunately the HFR value used for the Bahtinov focus assistant does not have a unit, that will make predicting how much you need to move the focus to get perfect focus difficult. Example: You can NOT say for instance that when the HFR value for Bahtinov focus is 1.2 the you need to move your focuser a certain amount of micrometer to get to perfect focus.
I think just like with the other auto-focus methods, a scan is done from one focus position to another to create a curve, then the lowest point in that curve is the optimal focus position. The same works for the Bahtinov auto-focus too.

I hope this will answer your question sufficiently.

Kind regards,
AstroRunner
The following user(s) said Thank You: AstroMuni
1 year 7 months ago #85261

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In effect you are saying that when I select the Bahtinov mask option, the graph is NOT showing HFR but a representation of the offset, right?
Last edit: 1 year 7 months ago by AstroMuni.
1 year 7 months ago #85262

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Hi AstroMuni,

Yes, that's right. For the Bahtinov focus the HFR labels should actually say something like "Offset". That would have been less confusing.

Regards, AstroRunner.
1 year 7 months ago #85268

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I am using Kstars 3.6.0 on Linux Mint and I get this pattern when I choose the Bahtinov mask option. What do all these numbers mean? And what am I doing wrong. I thought once I select the star I should start seeing 3 lines and an offset reading for central line.
Last edit: 1 year 7 months ago by AstroMuni.
1 year 7 months ago #85289
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Hi AstroMuni,
I would expect that after you selected a star in the image, it would capture the image again and then indeed show the 3 lines. From your question I understand that has not been the case. You can try to click the capture button again to force taking a new image and make the Bahtinov calculation. If it still fails, can you look at the log messages at the bottom of the window to see if there is an error?
I haven't been able to check Kstars version 3.6.0 for myself yet. But I will give it a try as soon as I have more time for it.
Regards, AstroRunner
1 year 7 months ago #85297

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No, there were no errors showing up. I clicked many times and even tried the loop and Autofocus buttons. Same result :-( Stumped!
If I get the opportunity I will try out on my RPi too as that still has older version of Kstars 3.5.9
Last edit: 1 year 7 months ago by AstroMuni.
1 year 7 months ago #85298

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