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Autofocus and bahtinov masks with filters

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#1 WSMIKE

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Posted 26 January 2022 - 04:23 PM

Hi
I was wondering if one can double check autofocus results with bahtinov mask in all filters including narrowband. I would need to order a bahtinov mask so before I do I’d check with everyone’s experience.

#2 crowley213

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Posted 26 January 2022 - 05:03 PM

I only have the 2” Optolong L-Pro filter, not a real narrowband filter, mounted in the flattener of my WO Z61II and it works to focus with the Bathinov mask that is integrated in the telescope cap. But it definitely needs a bright star to get a good visible cross from the mask.

 

Herbert


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#3 TelescopeGreg

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Posted 26 January 2022 - 05:38 PM

As Herbert said.

 

I would add that instead of ordering a Bahtinov mask for the quick check, you can make one simply enough if you ask your kids nicely to borrow some of their arts & crafts supplies.

 

https://www.deepskyw...tinov-mask.html

 

I used black construction paper for the mask, with the white printed paper glued to one side for cutting.  Works well, even without the autofocuser (used mine for several years).



#4 fewayne

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Posted 26 January 2022 - 05:41 PM

If you're using it to check, yeah, it works well. For actually achieving focus, the long exposure times necessary decouple the hand-eye-screen loop pretty badly, at least with rig. For focusing I pin the gain to the peg and bin 2x2 or 4x4, but NB images still take several seconds to show spikes.



#5 WSMIKE

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Posted 26 January 2022 - 06:26 PM

Has anyone tried the tri-bahtinov mask?


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