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Older Kowa TSN-3 performance? (1 Viewer)

jring

Well-known member
Hi,

you have to look for a trace (or rather the absence of it) between the 3rd and 4th reflections as the TSN-3/4 have a Steinheil design doublet with the CaF2 element (which takes the role of the crown glass here) as the back element and a crown glass (usually BaK5 - it takes role of the flint here) at the front.

Only Takahashi has so far dared to offer a Fraunhofer style doublet objective with a CaF2 front element in their FS series - and only in the early nineties after their friends at Canon-Optron (who makes the fluorite objectives for Takahashi and Kowa) had learned how to coat CaF2.

Joachim
 

Binoseeker

Mostly using spectacles (myopic) with binoculars.
No fake!

Thanks for explaining, Joachim,

Ok, so it was no trace between 3rd and 4th reflections, thus no fake.
Is the TSN-883/-4 lenses made the same way?
 

Binoseeker

Mostly using spectacles (myopic) with binoculars.
Ok,
Is there a cheaper alternative to the expensive rubber eyecup with integrated protective window, that fits the x30wide eye piece, TSE-14W ?
 

jring

Well-known member
Ok,
Is there a cheaper alternative to the expensive rubber eyecup with integrated protective window, that fits the x30wide eye piece, TSE-14W ?

Hi,

not quite sure what you mean. The current 30x wide EP for the small body Kowa (including the old TSN-1/2/3/4 series) is called TE-14WD (sometimes also TSE-14WD) and has a twist up plastic eyecup. I have not removed that to check if it contains an optical window in some way but would be most astonished if it did.

Or do you mean the old 30x wide which indeed has a fold-down rubber eyecup - but I only know that from images and would be astonished if it did contain an optical window.

Joachim
 

Binoseeker

Mostly using spectacles (myopic) with binoculars.
Ok,

The TSN-CV66 is an expensive eyecup, with protective window integrated, for also the older x30W, with fold down eyecup.

Here is a text from kowa website about TSN-CV66:
Also compatiable with many historical models. Compatible with current TSE-9Z (20-60x) eyepiece and TSE-14WD (30x).

I am looking for a cheaper normal fold-down eyecup for TSE-14W :)
 

jring

Well-known member
Hi,

I don't think that this is an actual eyecup but some kind of cover to go over the twist up eyecup of the current small body 30x wide and zoom EPs and protect the eyelens from whatever....
I also don't think that this is going to be compatible with older EPs with rubber eyecup.

If you need the actual eyecup I would mail Kowa and ask if there is still old stock available...

If that is not an option, you could measure the diameter of your EP and try to get a generic eyecup from astro accesories.

Joachim
 

henry link

Well-known member
Thanks for explaining, Joachim,

Ok, so it was no trace between 3rd and 4th reflections, thus no fake.
Is the TSN-883/-4 lenses made the same way?

The TSN-883/4 have a different objective design. In those the Fluorite element is the interior lens of a fixed triplet combined with a moving focusing doublet. See the cutaway below.
 

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Binoseeker

Mostly using spectacles (myopic) with binoculars.
Ok, thanks,
I got some info from Kowa: the fluorite lens on tsn-3/4 is single coated.
 

jring

Well-known member
Hi,

first of all, thank you Henry for sharing the info on the 883!

As for the single coated fluorite element - possible on your late example, not so much on mine from the eighties. Will check when back from the tropics...

Joachim
 

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