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Old 13-09-2013, 12:16 PM
PeterHA (Peter)
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Takahashi optimised for mirror or prism

Some designs of refracting scopes (Zeiss) take a glass path like a prism star diagonal into consideration when the optics are designed.
Other designs are optimised to perform best with mirros star diagonals.

Does anyone know what Takahashi bases it's optical calculations for refractors on.
Are the Sky90, TS-102 and 120 better used with prism diagonals or with mirror diagonals?

Thanks for any help,


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Old 13-09-2013, 12:29 PM
brian nordstrom (As avatar)
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Hi Peter , I have a SKY90 and use it with a 2 inch , GSO Quartz 99% dielectric and I find this diagonal to be very good in this scope , better than my Zeiss prisim diagonal but I cant use the GSO in the Zeiss as its 1 1/4 inch only .
The Zeiss prism diagonal is better than my William optics 99% diagonal in my Zeiss tho , less light scatter around brighter objects with the Zeiss prisim diagonal and more natural tones ( in my eyes ) on the moon , perfect ! .
Hope this helps .
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Old 13-09-2013, 02:45 PM

Kunama is offline
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Some references indicate that they are based on the prism however Tak also do a mirror.
I am going to get the 1.25" Tak prism for my new FS60CB (mainly for the non-marring, self centering eyepiece clamping feature).
On the TSA120 I am using the WO 2" dielectric mirror (came with the scope) but will be switching this to the Baader Click-lock in the future (for the same reason)
I find that the WO actually tilts the EP when tightened.

Last edited by Kunama; 13-09-2013 at 05:44 PM.
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Old 13-09-2013, 04:51 PM
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Ebotec Alpeht Sicamb

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Centering the eyepiece isn't nearly as important as holding it parallel to the optical axis, BTW. The clamps don't help in that regard, but the Glatter Parallizer does.

I find that the Tak prism produces visibly less scatter than any of the mirror diagonals I've used in my 6" Mak.

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mirror, prism, refractor

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