Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

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blauvista
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Joined: Sun Feb 06, 2022 12:00 pm

Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#1

Post by blauvista »

Hi, I would like to make a request. The current Bahtinov Mask Focus Aid is thrown completely by a Tri-Bahtinov mask. Do you think you would be able to add this as an addition = 9 line detect rather than 3 line detect? Since the tool clearly measures the angles between the lines (to give the score) a separate score for each of the 3 pairs or a readout of the angles (rather than score) would allow not just accurate focus but also collimation = the three scores should be the same for accurately collimated scopes. For my own use this would be a great aid (and perhaps for others as well).

Many thanks, Mark
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admin
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#2

Post by admin »

Hi Mark,

if you could post some sample images that show 'perfect' on the mask and the various different 'bad' situations, then I will investigate. Detecting the lines is relatively easy, but the interpretation of the different arrangements may be harder!

cheers,

Robin
blauvista
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#3

Post by blauvista »

Hi Robin, i never got any "perfect on the mask" hits., One of the outer lines generated by SharpCap always seems to get pulled way way off by the other lines /structures that are visible. This is only very briefly visible before the almost constant message: "3 lines detected but angles are not the same" re-appears. I have attached a typical out of focus tri-bahtinov mask image (Copied from internet - not mine!). i am sure not easy but certainly really worthwhile ... All the best, Mark
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Borodog
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#4

Post by Borodog »

+1 this feature.
GSchreider
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#5

Post by GSchreider »

I also second this request.
It would be a great feature to support collimation of SC especially.
There is a Github project called Tri-Bahtinov grabber https://github.com/1CM69/Tri-Bahtinov_Grabber
It looks like this project is not active anymore and there are no executables but only source code.
Maybe it could be re-used in some form.
Cheers
Gernot
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#6

Post by admin »

Hi,

thanks for sharing the link - I was not aware of that project previously, and I can see that it has a software license (MIT) that would be compatible with potentially including some code in SharpCap.

cheers,

Robin
Borodog
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#7

Post by Borodog »

+1
GSchreider
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#8

Post by GSchreider »

Hi Robin,

great that you are looking into this topic.
I do volunteer to test things if you want someone to look at it

Cheers
Gernot
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#9

Post by admin »

Hi,

as a first step in this direction I have tweaked the current bahtinov code so that it will highlight the lines detected on a tri-bahtinov image (but it will not try to work out the focus offset yet).

This will be in SharpCap 4.1, which I am hoping to release as a public beta sometime this week.

cheers,

Robin
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Re: Focus Aid/Collimation Aid - Tri-Bahtinov Mask recognition

#10

Post by Borodog »

Wonderful!

I would imagine that it would produce 3 focus scores, and in collimation these scores should be equal. That could lead the way to some sort of collimation scoring system that might not necessarily need the scope to be refocused after every change of a collimation screw, which is usually required because it changes the focus of all three patterns.
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