Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Unitron 40mm and 50mm scopes Cemented or Air Spaced?

  • Please log in to reply
65 replies to this topic

#1 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 09:53 AM

Please take a look at your Unitrons of 40mm and 50mm aperture, and post here if you find the objectives air-spaced or cemented.  We are not interested in the 40mm finder scopes found on larger Unitrons, just OTA objectives from 40mm and 50mm models.  Three foil spacers will be visible if air-spaced.  No spacers and it is probably cemented.  Please do not remove your objectives for this, unless you know what you are doing.

 

 

I have a 50mm model 105 from the 80's that is air-spaced.  I will check my older 40mm and 50mm models this weekend to be sure, but I remember testing them as cemented.  Stay tuned.

 

 

Thanks!

 

 

 

 


  • rcwolpert, Bomber Bob and Augustus like this

#2 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 09:59 AM

I am still surprised! The 42mm finder I had was very old, heavy, brass bodies, and an air-spaced objective. I have never seen a 127/740 up close but I do know that it was at the absolute bottom of the Unitron line while those 40mm finders went with their top-of-the-line telescopes. The 40s were probably considered ‘toys’ tho at 75 bucks they were quite expensive toys, around the same cost in 1965 as Mayflower 814 60mm alt-az scope, which was an excellent buy.

 

Johann, you have one of these 40mm scopes, check it out please. See if the objective is air-spaced.


  • Chuck Hards likes this

#3 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 10:16 AM

From one of my 50 y.o. Unitron catalogs. Note that it says the objectives are all air-spaced.

Attached Thumbnails

  • 2D9272E2-26C3-4806-8168-A137248402B6.jpeg

  • clamchip, Marc-Andre, rcwolpert and 1 other like this

#4 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • Posts: 24,152
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 24 January 2018 - 10:21 AM

all i got to do is find it. lol.gif


  • Terra Nova likes this

#5 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 10:29 AM

Classically a Fraunhofer achromatic lens mounted in a metal cell. With focal ratio f/17.5 for a 40mm objective, Chromatic Aberration to all intents and purposes can be considered invisible in the eyepiece. The CA index for this is a shade over 11 and I did not notice false color on any object of interest – the scope is purple/violet/indigo free. According to the rule of thumb, 2x per mm of aperture, the maximum useful magnification would be 80x. This rule of thumb does not apply to this scope at all – I can push 3x per mm of aperture before noticing “scope induced diffraction” fuzz at the eyepiece. This scope can easily tolerate a 6mm eyepiece, although views get fuzzy with a 5mm eyepiece. One can push 110 – 120x out of this scope with no loss of generality. Quality wise, this 40mm f/17.5 Unitron matches up to a very good 60mm f/13 - f/15 – both start huffing and puffing well beyond the so-called 2x per mm rule. As for diffraction patterns – airy disc of stars are exactly as expected for a quality instrument.”

 

From post #1, https://www.cloudyni...?hl=unitron 127



#6 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 10:35 AM

Spec sheet on the 50mm says air-spaced objective (P. 2), but this appears to be a later model. My older catalogs do not list a 50mm. They go from the 40mm model 127 ($75) to the 60mm model 114 ($125). (The models 740, 750, and 760 are a different kettle of fish. All 700mm f.l., and I believe, all later (1980?) with stick-on labelled rather than engraved focusers, although this one is model number 105?).

 

http://www.unitronhi...2014/09/105.pdf


Edited by terraclarke, 24 January 2018 - 10:41 AM.


#7 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 10:42 AM

That's why I'm asking for people to post actual examples.  From what I've seen, the Unitron literature isn't 100% factual.  

 

Surprised me too!  But then in the last few years, I've had a lot of classic bubbles burst.   


  • Jon Isaacs likes this

#8 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 10:45 AM

Ah ha! I knew I had seen this! A photograph of Brian G.’s model 127 42mm objective, and note the spacers!

 

(post #23) https://www.cloudyni...42mm/?p=4794697



#9 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 10:46 AM

I wonder if the first examples were air-spaced, and at some point they transitioned to cemented, as a cost-saving strategy.  shrug.gif

 

Cemented elements in and of itself isn't a sign of poor quality.  In fact it increases throughput by effectively eliminating reflections off two surfaces.  It is not done in larger sizes due to differential expansion rates of the two different objective glasses.



#10 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 10:51 AM

Terra, the 105 is a late model, I have a pristine example and it is air spaced.  I'm wondering about the early models.  I do have an early 50mm even though it is not listed in the catalogs at the time.

 

It's the early models I'm asking about.  



#11 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 10:52 AM

I wonder if the first examples were air-spaced, and at some point they transitioned to cemented, as a cost-saving strategy.  shrug.gif

 

Cemented elements in and of itself isn't a sign of poor quality.  In fact it increases throughput by effectively eliminating reflections off two surfaces.  It is not done in larger sizes due to differential expansion rates of the two different objective glasses.

Yes, Zeiss Telementor objectives are fine lenses and are cemented, but that is not what got us here. It was your inference in the other thread that the 40mm Unitrons were sub par and had cemented objectives. However, the several reviews that I have found today after an hour’s research point to the opposite- quality optics with air-spaced objectives. And they are the earlier model 127s (model 127 is the earliest model number for a sub60mm Unitron) with engraved focusers.


Edited by terraclarke, 24 January 2018 - 10:55 AM.


#12 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 11:05 AM

Terra, I just said that the three I tested were not top-quality.  I can only report on what examples come my way.  Based on my experience, I can't say all Unitron objectives of 40mm and 50mm aperture are high-quality.

 

That's why I want other owners to chime-in and let us know what is actually out there.

 

I hate it when a maker's reputation takes a dive, but I can only report what I know to be true personally.  

 

So as of now, we have reports going both ways.  We need more data.


  • Jon Isaacs and DAVIDG like this

#13 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 11:20 AM

Just for the record, I have tested seven Unitron astronomical models under DPAC from 40mm to 60mm, and four spotting scopes, one 70mm and three 80mm.

 

Of the seven astro models,  only one 50mm and three 60mm were good under DPAC, and only one of those would I consider very good.  I did tell a member in a PM yesterday that the little 40mm scopes still put up good images for their aperture, I'm guessing because Dawe's limit is easy to hit at 40mm.  The late model 105 50mm from about '82 tested good and is air-spaced.

 

The spotting scope models, all short-focus and cemented, tested OK but with some spherical abberation, as is to be expected with a short doublet. 

 

I repeated all tests because I had a lot of trouble wrapping my mind around the concept of Unitron putting out anything less than excellent.  It still makes me shake my head in wonder.


  • DAVIDG and Bomber Bob like this

#14 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • Posts: 24,152
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 24 January 2018 - 11:26 AM

of course there is always the possibility those cemented objectives are not original to the OTA


  • Terra Nova likes this

#15 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 11:31 AM

Could be, but three all coming to the same second-hand owner?  And all the proper focal length?   Most 40mm scopes of the day used internal erectors.  The native focal lengths, minus the erectors, is much shorter than a stock Unitron.

 

This is what I'm trying to ascertain.  If we get posts of other cemented objectives, it would make me lean less toward the swapped-out theory.  No other examples would lend credence to them having been swapped-out.


  • Jon Isaacs likes this

#16 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 12:18 PM

imawake.gif


  • starman876 likes this

#17 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 24 January 2018 - 12:28 PM

Yeah, it might take a while.  :lol:


  • Terra Nova likes this

#18 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 01:14 PM

If native to Unitron, I would be more inclined to think it a relatively late phenomenon.



#19 CharlieB

CharlieB

    Fly Me to the Moon

  • *****
  • Posts: 5,554
  • Joined: 11 Dec 2007
  • Loc: Southern NH

Posted 24 January 2018 - 01:15 PM

The two 105s and the 127 of mine are air spaced.  Even the two SPI 40s have air spaced objectives as are the 40mm RAOs.  

 

The 105 objectives are superb and the 127 is good, but nowhere near the 105s.  The SPIs are fair and the RAO 40/500s are excellent.

 

Charlie


  • starman876, Terra Nova and Bomber Bob like this

#20 deSitter

deSitter

    Still in Old School

  • *****
  • Posts: 12,129
  • Joined: 09 Dec 2004

Posted 24 January 2018 - 01:36 PM

My 40mm RAO is also air spaced and excellent.

 

-drl



#21 Bomber Bob

Bomber Bob

    ISS

  • *****
  • Posts: 20,242
  • Joined: 09 Jul 2013
  • Loc: The Swamp, LA (Lower Alabama)

Posted 24 January 2018 - 06:47 PM

It's an obvious question (and I'm just the old dude to ask it):  Are the scopes with cemented objectives branded UNITRON, or Polarex, Weltblick, etc.?  If yes, do they all use the same font / style?  Same lens specifications?

 

I could see an N-S supplier -- the same supplier -- doing something like that with these smallest objectives.

 

I could also see previous owners cleaning their lenses, losing the spacers, and cementing the elements.  The 152 I owned for a bit was missing spacers.

 

Lots of stuff can happen to these scopes over the decades.


  • Chuck Hards likes this

#22 Dave Trott

Dave Trott

    Ranger 4

  • *****
  • Posts: 343
  • Joined: 30 Dec 2009
  • Loc: Colorado

Posted 24 January 2018 - 09:06 PM

I have a 740,750 and 760. Those are from the 60's. All have spacers. I also have a very old 127 with no spacers. I don't remember the details on the optical performance of these scopes but the quality of the optics is at least acceptable on all of them or I would remember it.

 

Is it possible that Unitron started to promote "all air spaced objectives" at some point in time?

 

- Dave


  • starman876, Terra Nova and Bomber Bob like this

#23 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 24 January 2018 - 09:28 PM

My 1966 catalog shows the 127 but has ’Discontinued’ stamped across the picture. There are no 700-series scopes listed. I have a couple of other catalogs that I will dig out and check tomorrow.



#24 Terra Nova

Terra Nova

    ISS

  • *****
  • Posts: 25,583
  • Joined: 29 May 2012
  • Loc: 39.07°N, 229m AMSL, USA

Posted 25 January 2018 - 06:58 PM

I checked a couple of earlier Unitron catalogs today; they had the 40mm x 700mm model 127 listed but no model 7XXs.



#25 Chuck Hards

Chuck Hards

    You don't know Swift from Astrola

  • *****
  • topic starter
  • Posts: 27,694
  • Joined: 03 May 2010

Posted 25 January 2018 - 09:55 PM

I've never seen any 7XX models in any catalogs either.  I wonder if going through old S&T's would bear fruit?  

 

The searchable DVDs won't run in my new computer for some reason.  I'll try them in my wife's laptop.  My paper copies are boxed and buried in the basement except for recent ones.


  • Terra Nova likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics