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Tri-Bahtinov masks ......... any good ??

Craney

By Craney
in Imaging - Discussion

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Craney

Craney

Posted
Posted (edited)

Hello everybody,

Have not really posted for a while.   Lock-down has impacted my job to the extent I am working more hours than ever.    The astro stuff has taken second place to sleep and recuperation....oh and re-decorating the house from bottom to top. ( !!🥴)

Anyway, when I do get out,  I find that for sake of completeness I like to check the collimation and focus of my SCT.    Lots of twiddling of Bob's knobs ensues etc... you probably know the score.

When I saw this item    
A Tri-Bahtinov mask for SCT collimation and focusing - Equipment - Cloudy Nights

I became intrigued and wondered if I could proverbially kill the two birds with one stone.   Since they are not mentioned very often I was wondering if they were more trouble than they were worth ?

As anybody found long lasting success with this device and use it as their 'go-to' collimation / focus tool  ??

( i followed a thread on CN which started off well and then descended into a technical discussion of how to print them off..... not actually if they were any good !!! )

Many thanks for any experience or insight.

Cheers,

Sean

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Craney

Craney

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Yes..... just watched it through.  Yes.... not conclusive.

 It would be really nice to see somebody take a uncollimated scope and put it through a Tri-mask collimation routine and quickly arrive at an arrangement that could not be improved upon by any  fancy Hotech  laser technique  or such.

Is it my eyes or is there a slight wobble on the middle spike of each cluster as the scope comes into focus ?  (How would you get precise and repeatable results if your 'bench-mark' is prone to movement).

How do you know whether  it is the  collimation or the focus that is splaying your lines ??

hmmmm ???

 

 

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  • 1 year later...
recceranger

recceranger

Posted
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On 29/01/2021 at 12:33, Craney said:

Hello everybody,

Have not really posted for a while.   Lock-down has impacted my job to the extent I am working more hours than ever.    The astro stuff has taken second place to sleep and recuperation....oh and re-decorating the house from bottom to top. ( !!🥴)

Anyway, when I do get out,  I find that for sake of completeness I like to check the collimation and focus of my SCT.    Lots of twiddling of Bob's knobs ensues etc... you probably know the score.

When I saw this item    
A Tri-Bahtinov mask for SCT collimation and focusing - Equipment - Cloudy Nights

I became intrigued and wondered if I could proverbially kill the two birds with one stone.   Since they are not mentioned very often I was wondering if they were more trouble than they were worth ?

As anybody found long lasting success with this device and use it as their 'go-to' collimation / focus tool  ??

( i followed a thread on CN which started off well and then descended into a technical discussion of how to print them off..... not actually if they were any good !!! )

Many thanks for any experience or insight.

Cheers,

Sean

Hi Sean,

Just wondering if you drew any conclusions about these masks for SCT's. I have a C9'25 and am considering giving it a go. Not sure were or if I should purchase though?

Rick

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Craney

Craney

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Hi Rick,

No sorry, never really followed it up and have  fallen back to using the traditional star test and lots of cold bruised finger tips to get my 8HD  'sort of'  collimated with Bob's knobs.

My feeling is that if this 'TRI-MASK' method was a tremendous step forward then everybody would be singing its praises.......  the silence suggests that maybe it does not quite meet the level of precision preferred by  astro types.

Then there is the new kid on the block.   The  OCAL

https://www.firstlightoptics.com/other-collimation-tools/ocal-electronic-collimator-pro.html

That can be done in daylight.....

Expensive though, but will sort out my  Newtonian F4's as well.... and maybe the RC.

 

Sean.

 

 

 

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tomato

tomato

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Do the radial set of lines indicate not only correct focus but also good collimation? If so, then IMHO they are a step up from the the original, but it would mean you’ll spend time collimating before focusing whereas with the original you would focus in blissful ignorance…

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Same old newbie alert

Same old newbie alert

Posted
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3 hours ago, david_taurus83 said:

The NE and SW spikes look like they need a small tweak but the rest are spot on. What's going on there?

Yes you're quite correct David, I noticed that they wasnt quite right in the pic the following day, so gave the collimation screws a little tweak and bobs your uncle Dave.  

I must check it as that's quite old now, shouldn't think it's changed as the scope hasn't come off the mount since

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Annehouw

Annehouw

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1 hour ago, gorann said:

I found this rather recent video on Youtube with a guy that seems very happy with his tri-Bahtinov mask. Just a pity he did not say how to get hold of one.

 

The configuration of the slit pattern is somewhat f ratio dependent. I first cut out  one myself out of thick cardboard (lots of work) and later had one laser cut from a thin sheet of aluminium to get sharper lines (local supplier).

Here is the calculator https://satakagi.github.io/tribahtinovWebApps/Bahtinov.html

 

It works more or less for me. Good seeing helps a lot. I can get close, but at f/3 it is not the last word in collimation.

 

CS Anne

Edited by Annehouw
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gorann

gorann

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I just ordered three of them from Farpoint, one for the RASA 8, and one for each of my Edge HD 8 and 11. But 65 USD for shipping from the US was a bit stiff, but that is apparently how the world works nowadays. I will try it on the RASA first, since my Edges are not on any mounts right now.

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Craney

Craney

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Hi Goran,

It's been over a year since I posted this question / discussion.

Did you have any success with the Tri-Bahtinov  ??    Would you recommend it over other methods ??

Cheers,

Sean

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gorann

gorann

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8 hours ago, Craney said:

Hi Goran,

It's been over a year since I posted this question / discussion.

Did you have any success with the Tri-Bahtinov  ??    Would you recommend it over other methods ??

Cheers,

Sean

I have to admit that I have not used it yet since my RASAs appear to have kept their collimation. Now I have lost astrodarkness so it will not happen for a while. Sorry!

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Craney

Craney

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1 hour ago, gorann said:

I have to admit that I have not used it yet since my RASAs appear to have kept their collimation. Now I have lost astrodarkness so it will not happen for a while. Sorry!

No problems.    I see that you can buy them from RV Optics.    Might give them a ring and see which ones best for my 6" RC.   Worth a go.

Sean.

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