Thoughts on three vintage 1980’s spotting scopes (1 Viewer)

[tonytoned]

Hello Everyone

I have a Mirador 1560 15-60×60 in nice condition. It is practically identical to the Bausch and Lomb Discoverer 15-60x60.
My Mirador 1560 15-60x60.


The Discoverer. Bausch and Lomb 15-60x60.

My question and thoughts are, I also had a Swift Telemaster 15-60x60 spotting scope back in the early 1980's. Do you think there is much difference in the optics considering they are probably all manufactured in Japan. They are all similar in dimensions and construction, apart from the focusing recess wheels on the Swift.



I think for their age the optics are very good, obviously except at a higher magnification. But what scopes don't suffer from that nowadays, unless it's your top end scopes.

I look forward to hearing about your thoughts. Thank you for your time.

 

[jring]

Hi,

nice collection of interesting vintage spotters... probably all related. I found an instruction leaflet for the Bausch & Lomb model here:

https://www.bushnell.com/on/demandware.static/-/Library-Sites-HuntShootAccessoriesSharedLibrary/default/dw65ab154c/productPdfFiles/bushnellPdf/Product%20Manuals/Spotting-Scopes/PDF/78-1600_Discoverer.pdf

My TSN-3 is also from the 80s, albeit second half... and was definitely a top end scope back then. And since it's a cherry it's still quite usable at 84x if needs be.

Since those probably are all fairly fast achromatic doublets at f7 or so, I would expect the image to get gradually softer beyond 40x... the question is how narrow the apparent field of view is at 40x... They don't look like having classic zoom EPs but rather some telephoto like objective design and a fixed (and hopefully wide angle) EP... like the Zeiss Harpia...

Joachim

 

[Binastro]

Mirador are usually better.

Regards,
B.

 

[Elkhornsun]

There has been a dramatic improvement in optics over the past 40 years, thanks largely to the designers having the use of computers, but also to improvements in lens coatings. New plastics have also been developed that are thermally stable and a lot lighter than metal. New optics also have much better weather sealing and anti-fog performance.

 

[Merlin]

Hello Everyone

I have a Mirador 1560 15-60×60 in nice condition. It is practically identical to the Bausch and Lomb Discoverer 15-60x60.View attachment 1586273View attachment 1586274
My Mirador 1560 15-60x60.

View attachment 1586277
The Discoverer. Bausch and Lomb 15-60x60.

My question and thoughts are, I also had a Swift Telemaster 15-60x60 spotting scope back in the early 1980's. Do you think there is much difference in the optics considering they are probably all manufactured in Japan. They are all similar in dimensions and construction, apart from the focusing recess wheels on the Swift.

View attachment 1586276

I think for their age the optics are very good, obviously except at a higher magnification. But what scopes don't suffer from that nowadays, unless it's your top end scopes.

I look forward to hearing about your thoughts. Thank you for your time.

I still have my Swift Telemaster and the adaptors for taking photos through it with my OM10. I also had the Swift Telemaster 'Junior' which was a much smaller and obviously cheaper, sadly I gave it away when I acquired the larger version.
I sometimes use it for old times sake, it is somewhat heavy but I remember it with affection as I carried it throughout the World and all the amazing birds and wildlife that I saw through it. I would never part with it.

regards
Merlin

 

[jring]

There has been a dramatic improvement in optics over the past 40 years, thanks largely to the designers having the use of computers, but also to improvements in lens coatings. New plastics have also been developed that are thermally stable and a lot lighter than metal. New optics also have much better weather sealing and anti-fog performance.

Hi,

I tend to say the opposite... there have not been signifcant improvements in optics in the last 30 years... last 40 there was two and those two were mainly about roof prism bins... see below.

• multicoatings were getting mainstream in the early 80s
• ED glass was mainly unavailable in the early 80s but CaF2 crystal elements started to move from Canon's photo lens department over to Canon Optron and then to their customers Takahashi (FC series in 81 - not counting the ultra rare TS-90 fluorite triplet from 71) and soon after Kowa (TSN-3/4 in 86).
• raytracing software for simulating lens and/or eyepiece designs dates back to the 70s... Accos, Code V and Sigma to name a few ones... not quite as easy to use as current suites but still very powerful tools in the hands of a good designer. Certainly sufficient for simulating complex systems with surface numbers in the lower tens... as long as you kept to spherical surfaces. Since aspheric surfaces are even nowadays mostly avoided unless it's either cheap plastic lenses or big astro scopes, this was not a limitation for sports optics.
• phase coatings were actually only available in products in the early 90s. Same goes for dielectrical mirror coatings for roof prisms. Both of these are only relevant to get roof prism designs to compete optically with porros thus enabling more compact binoculars of not too much worse quality than a good porro pair.
• new materials for building lighter and/or more weatherproof bodies are nice but not really an advance in optics.

Joachim

 

[Binastro]

Alan Turing around 1951 was looking for difficult tasks for his computers.

Prof. Charles Wynne jumped at the chance and used this for lens design.

I think first at Manchester, but also at other sites.

Around 1955 the US was also attempting this work but it was classified.

Although Charles Wynne also did classified work, some of the lens programmes that he invented with Nunn were open source and got funding, so Britain were the leaders in the field.

Zeiss were still using old fashioned approaches.

By 1959 Wynne's programmes were in full use and these programmes are still used today.

In 1951 while at Wray Wynne designed the 50mm f/0.71 lens and 64mm f/0.71 lens that were used for mass TB x-rays in mobile vans. I probably had one of these x-rays about 1952.
They were recorded on 35mm film.

So computers were being used for lens design in Britain in the 1950s.

Regards,
B.

 

[Binastro]

Binoculars were generally lagging behind lenses, but Liechtenstein were double coating in the 1940s.

TTH patents for three layer tunable coats are from around 1960.

All surfaces including cemented surfaces were coated.

I suppose the thorium glass in the 1941 Kodak Aero Ektar is ED glass.
First developed in the late 1930s.

In fact Taylor's 1890s telescope objectives had early ED glass, but it was found to need repolishing every 7 to 10 years depending on humidity.

These telescopes were used worldwide for star surveys.

Michael Faraday invented various glass types including ED type glasses.
These eventually ended up being made by Zeiss, freely given.

Regards,
B.

 

[Binastro]

Unfortunately thorium glass does turn up in early Kodak military eyepieces and also in some Japanese orthoscopic eyepieces from the 1960s.
Swift and no name examples.

Also in numerous photo lenses.

I would avoid using the Wray 50mm f/1.0 lens as an eyepiece as it has zero eye relief.
The rear element is thorium glass.

B.

 

[jring]

I suppose the thorium glass in the 1941 Kodak Aero Ektar is ED glass.

Hi,

I suppose we have different definitions of ED glass then... the usual term is for stuff with Abbe numbers over 75 - see the left side of Fig 148 on this webpage... the x axis is Vd aka Abbe number.

REFRACTING TELESCOPE OBJECTIVE: SEMI-APO AND APO OBJECTIVES

Refracting objective: achromat and apochromat. Description, illustration, optical properties.

www.telescope-optics.net

I didn't find optical data for thorium glass but I did for not quite as bad lanthanium glass which replaced it later... e.g. early 50mm f2 Leica Summicrons used thorium glass which was later replaced with an inhouse lanthanium crown glass which was later licensed to Schott and marketed as LAK9.

Rare Earth Glass Leica Lenses: A Quick and Quirky Overview — LSI - Leica Society International

Yes, they were (and still are!) literally radioactive, but they incorporated elements made of thorium and lanthanum glass because of their unique optical properties By Jason Schneider By the late 1940s, the management at Leica knew they needed to come up with a superlative successor to the well-re

leicasocietyinternational.org

We have data for that, in fact it can be found on the chart mentioned above on the lower right... LAK8 is fairly easy to find a bit above the green sweet spot lines for ED doublets at Abbe number 53 or so, LAK9 is the lower blue dot at the cluster a bit to the left, right on the lower one of the red diagonals at an Abbe number of around 55... or use the magnification of that busy area, LAK8 and LAK 9 are in the right upper corner.

So yes, thorium and lanthanium glass were used for their low dispersion but are quite a bit away from what we call extra low dispersion today. The latter just contain liberal amounts of flurorides which shifts their properties close to those of CaF2 or fluorite crystal...

Joachim

 

[jring]

Unfortunately thorium glass does turn up in early Kodak military eyepieces and also in some Japanese orthoscopic eyepieces from the 1960s.
Swift and no name examples.

Also in numerous photo lenses.

I would avoid using the Wray 50mm f/1.0 lens as an eyepiece as it has zero eye relief.
The rear element is thorium glass.

Hi,

thorium in EPs is kinda criminal - the main isotope Th 232 is an alpha emitter and thus not a problem unless ingested, inhaled or in direct tissue contact (as in pressing the thorium glass rear element of an objective used as EP directly to your eye), but further down the decay chain there is a very energetic 2.6 MeV gamma decay which goes through almost anything and is NOT what the doctor ordered usually...

Joachim

 

[Tringa45]

thorium in EPs is kinda criminal - the main isotope Th 232 is an alpha emitter and thus not a problem unless ingested, inhaled or in direct tissue contact (as in pressing the thorium glass rear element of an objective used as EP directly to your eye), but further down the decay chain there is a very energetic 2.6 MeV gamma decay which goes through almost anything and is NOT what the doctor ordered usually...

I can understand the environmental concerns in production but think personal fear is unfounded.
After 29 Gigabecquerel of intravenous lutetium 177 over the past eight years I would not give a second thought to using an instrument with thorium glass!

John

 

[chill6x6]

I can understand the environmental concerns in production but think personal fear is unfounded.
After 29 Gigabecquerel of intravenous lutetium 177 over the past eight years I would not give a second thought to using an instrument with thorium glass!

John

So more importantly, how are you doing?

 

[Binastro]

I had about 12 Aero Ektars under my bed for years, which started my interest and resulted in papers on thorium glass in lenses.

I monitored over two thousand lenses and about one hundred were radioactive int the late 1970s and 1980s.

Horace Dall had a large slab of glass on his work bench, which was his optical flat.
When I pointed out it was thorium glass he wasn't the slightest bit concerned and it remained on his work bench.

I personally would not use a full thorium glass right up against my eye as the biological results were not available in the 1980s.

British optical firms did clean up their premises, where large amounts of thorium glass were present.

Also the Ministry disposed of their stocks of these lenses.

The glass makers refused to discuss this matter.

Also, I don't know if workers making these lenses were at risk.

Quite a lot of the young women who hand painted radium on watches in Chicago did die from this work.

I have been told that dentists made up amalgam by rubbing the compounds up between their bare hands and this resulted in mercury poisoning.

I could detect the radiation from the rear element of the 24inch f/6 Aero Ektar at 6ft.

There are now regulations regarding these lenses and they cannot be worked on and thorium glass is no longer allowed in normal lenses.
There are also storage limits.

Regards,
B.

 

[Tringa45]

So more importantly, how are you doing?

Thanks for asking, Chuck. Well, it's winning slowly but is not particularly aggressive and well differentiated as they say.

Regards,
John

 

[chill6x6]

Thanks for asking, Chuck. Well, it's winning slowly but is not particularly aggressive and well differentiated as they say.

Regards,
John

John,
Praying for ultra-slow progression and a great quality of life. There are still plenty of tripods and scopes still out there to keep you busy..

I also want to add I appreciate the knowledge and experience on scopes, tripods, and binoculars, etc. A wealth shared of knowledge.... Thank you!