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Why didn’t TeleVue ever offer another triplet?

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#1 Terra Nova

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Posted 10 January 2022 - 11:11 AM

I wonder why Al Nagler never offered another refractor with a Triplet objective after the Oracle? Like a 4” particularly? I understand that he was fully invested in the Petzval concept but he did come out with the TV102 apochromatic doublet and also the TV85 of similar design but faster focal ratio. Being the optical designer genius that Al is, it surprises me that he didn’t produce something in the 90mm caliber as a triplet in competition with the Brandon 94 and AP Stowaway. Why stop with the Oracle, which owners say was a fine lens, (I’ve never seen one close-up)?



#2 astrokeith

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Posted 10 January 2022 - 11:27 AM

A good question. I wonder if someone here has asked him!

 

I might guess he didnt want to do any more 'fast' scopes and as such didnt see the need for a triplet? (I know f7 isnt fast by some standards!)


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#3 Spikey131

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Posted 10 January 2022 - 11:28 AM

I’m pretty sure that I read somewhere (yeah, I know, take it with a grain of salt) that the Oracle was abandoned due to excess cost.  So when the newer glasses became available, he could build a better small telescopes as doublets.  So we have the TV60, TV76 and TV85.

 

And then Al built the Multipurpose Telescope (a 5” Petzval) in order to have a well corrected, flat field platform to test eyepieces.  So from the MPT concept he developed and perfected the large Petzvals which culminated in the NP101is and NP127is.  These are practically unique in the high end telescope market, so his only direct competition are the very expensive Takahashi Petzvals (which are mainly astrographs).

 

The real question is why he never made a smaller Petzval astrograph, which would find a market among astrophotographers.


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#4 Bill Jensen

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Posted 10 January 2022 - 11:38 AM

Per the Company 7 website summary on the Oracle, the cost of producing the triplet caused the shift to the doublet 

 

"However, the difficulties of producing high performance triplet apos, and rising costs resulted in the discontinuation of the "Oracle".

 

quoted in the overall summary of the history leading to the TV76

http://www.company7....copes/tv76.html

 

I like my Oracle, basically use it when I grab it to travel a few miles to show the grandkids the moon, planets and brighter objects. I am sure that the newer optics available are better but it works for me. 


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#5 Terra Nova

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Posted 10 January 2022 - 12:04 PM

I like my Oracle, basically use it when I grab it to travel a few miles to show the grandkids the moon, planets and brighter objects. I am sure that the newer optics available are better but it works for me. 

A thought that is mirrored by many of us who own an older TeleVue. My two still give me a great deal of satisfaction and are used regularly.


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#6 rexowner

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Posted 10 January 2022 - 12:04 PM

...

The real question is why he never made a smaller Petzval astrograph, which would find a market among astrophotographers.

Maybe they felt they had their bases covered with the TV-76 and TV-85 for visual only, and addding

a field flattener covered astrophotography.  Just a guess.



#7 Unknownastron

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Posted 10 January 2022 - 04:44 PM

I don't know about larger triplet-lensed  telescopes but I did ask Al why he quit making the Oracle.  He said the problem with a triplet was if any one of the three elements was off it usually meant you couldn't use any of the elements in another as they were all matched by hand.  Thus extra expense.  I asked because I have an Oracle which is a very fine telescope.  In fact, it was used by John Wagoner for observations when he compiled the Double Star Observing Certificate for the Astronomical League.

Clear skies and clean glass,

Mike


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#8 photoracer18

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Posted 10 January 2022 - 06:07 PM

Nobody has mentioned the TeleVue 140 F5 Petzval from 1996.




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