What's inside a Lunt CaK module?

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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thesmiths
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What's inside a Lunt CaK module?

Post by thesmiths » Wed Jun 27, 2012 11:05 am

I found the interesting mod describing how to convert a Lunt CaK diagonal into a straight through (in order to solve the back focus problem with some focusers) Lunt CaK B1200. It made we wonder exactly what the module consisted of and how it works. Does anyone know? Here are some of the photos from the mod page:







I have looked at the B1200 module but do not own one. There are two very reflective dielectric filters at each end of the long 2 inch tube (each a full 2 inch in diameter). Then there is the blocking filter at the back (with a 12mm diameter). As the two reflective filters are so widely spaced, I assume they are not acting as an etalon. I assume it works in a similar way to the PST CaK, which a number of people and disassembled and scrutinized.

My second question is could the blocking filter at the back be replaced with the Baader CaK filter? I have seen this mentioned with regards to a PST CaK mod. So, for example, could one take a Lunt CaK B600 diagonal (with a 6mm BF) and turn it into a straight through with a 30mm BF?

thesmiths
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Re: What's inside a Lunt CaK module?

Post by thesmiths » Wed Jun 27, 2012 6:45 pm

Vanter, from what the poster shows, the mod to create a straight through should not work since the filter they removed was actually not the narrow bandwidth blocking filter. But then perhaps the BF is in the eyepiece holder, which was reused. Since I don't (yet) own one, I can't really identify what is attached where.

colinsk
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Re: What's inside a Lunt CaK module?

Post by colinsk » Wed Jun 27, 2012 11:28 pm

I have found Lunt's posters to not be representational of the final products so be wary.
Thank you, Here are some references I have collected.



Etalon Article Part I

Etalon Article Part II

Solar Patents of interest

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Merlin66
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Re: What's inside a Lunt CaK module?

Post by Merlin66 » Thu Jun 28, 2012 4:37 am

Rusty,
ITF = Interference transmission filter...
I don't think there is a cak "etalon" in there...just the three filters tilted/ overlapping with a final narrowband blocker....
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.yahoo.com/neo/groups/ast ... scopy/info
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer

thesmiths
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Re: What's inside a Lunt CaK module?

Post by thesmiths » Thu Jun 28, 2012 10:19 am

I notice that the German language mechanical drawing is dated 14 July 1999, quite a bit before I think the product was even announced. So it could be not very accurate compared to what is actually sold today.

markthais
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Re: What's inside a Lunt CaK module?

Post by markthais » Fri Jun 29, 2012 1:18 am

Looking at the specs and drawings. They say the HW is 2.4Ang. But it looks like they are using an 60mmF/8 without any barlow or any other lens system, just hitting the band pass filter at F/8. Just from a guest I would say the HW is going to be broaden quite a bit, closer to an 6Ang filter. And if they are using only F/8 you can see they really need to knock down the energy. If not, it's going to get petty hot on that bandpass filter just because of the wavelength.
So am I missing something.
Mark

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Re: What's inside a Lunt CaK module?

Post by smerral » Sun Jul 08, 2012 10:37 am

Interesting. I have a B600 and I was actually going to do this mod but in the end I couldn't remove the blocking filter from the diagonal; I got one screw out but frustratingly not the other which appears to have been loctited - soft metal too so the head (allen key job) got knackered. In the end I gave up in case I did some damage.
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sullij1
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Re: What's inside a Lunt CaK module?

Post by sullij1 » Mon Jul 09, 2012 9:40 pm

Is there an adjustment for varying bandwidth in this unit or is it factory preset?
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