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Why 0.965”

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#1 Terra Nova

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Posted 08 February 2020 - 09:35 PM

If I once new the answer to this question, I have forgotten it in my acknowledged period of dotage. How did the obtuse 0.965” or 24.5 mm standard ever come about for eyepieces? If it started in a Metric System country why didn’t they just choose 25mm? If it started in an English System country, why not just 1.00 inches? Did no one like round numbers when they picked a standard? It just seems weird to me!


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#2 grif 678

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Posted 08 February 2020 - 09:41 PM

Never thought about it, but it is a good question. Maybe someone knows, I sure do not. I guess the same reason that Sears and others made the 76mm scope, why not 75mm?



#3 markb

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Posted 08 February 2020 - 09:42 PM

And why didn't it match the already in place microscope standard, too?


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#4 Terra Nova

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Posted 08 February 2020 - 09:46 PM

Never thought about it, but it is a good question. Maybe someone knows, I sure do not. I guess the same reason that Sears and others made the 76mm scope, why not 75mm?

I think because Sears was a very American company and 76mm or to be exact 76.2mm is exactly a nice round 3”, whereas, even tho Unitron was an American telescope marketing company, Nihon-Seiko is a very Japanese company and Japan was and is on the Metric System and 75mm is a nice round number. 


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#5 G-Tower

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Posted 08 February 2020 - 09:54 PM

I think Zeiss started using the .965 format since the late 1800's. Originally it may have been Huygens. Why? I have no clue.


Edited by G-Tower, 08 February 2020 - 09:55 PM.

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#6 Greyhaven

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Posted 08 February 2020 - 10:02 PM

Oh, some manufacturer  thought it would be good to match the 0.965 size of the focusers he had on the shelf in the warehouse.

Grey


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#7 Vesper818

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Posted 08 February 2020 - 10:53 PM

Maybe they fit in some original standard 1" OD tubing...
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#8 Kasmos

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Posted 08 February 2020 - 11:01 PM

I also heard it was Zeiss. I believe someone previously mention it on this site but I can't remember if they gave a reason for the size. undecided.gif


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#9 ccwemyss

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Posted 08 February 2020 - 11:08 PM

Maybe it was supposed to be 25.4 mm but the machinist was dyslexic, and after turning out a few hundred at 24.5, they decided to stay with it. smirk.gif

 

Chip W. 


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#10 GalaxyPiper

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Posted 08 February 2020 - 11:41 PM

Astrojenson said back in 20h August 2019 on Cloudy Nights

 

Microscopes have, to my knowledge, never used the 0.965"/24.5mm standard. They used the smaller 23mm barrel, which was a standard on continental microscopes well before WW1.

 

The Japanese telescopes copied the 24.5mm size eyepieces from Carl Zeiss, Jena, who had used this standard since 1897. Where they got it from is anybody's guess. Nikon, Goto and Nishimura all made refractors and accesories that were nearly carbon copy clones of Zeiss models. Nikon (or Nippon Kogaku, as their name was back then) even copied the pre-WW2 Zeiss adapter and quick-coupler program to such a minute degree that I suspect that parts are interchangeable, but I've never been able to confirm it.

 

Clear skies!
Thomas, Denmark

 

I think this might put it to rest. The question then goes to Zeiss and why they used that standard, or diameter. And it may be just a simple matter of trying to keep costs down in lens making and still making the telescopes useful.

Some decisions are made for economic reasons...

 

The other thread can be found here! https://www.cloudyni...-965-eyepieces/


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#11 Terra Nova

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Posted 08 February 2020 - 11:52 PM

^ “The Japanese telescopes copied the 24.5mm size eyepieces from Carl Zeiss, Jena, who had used this standard since 1897. Where they got it from is anybody's guess.

 

It’s still a mystery wrapped in an enigma, wrapped in a conundrum! :lol:

 

Inquiring minds want to know, ;)


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#12 GalaxyPiper

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Posted 09 February 2020 - 12:03 AM

It’s still a mystery wrapped in an enigma, wrapped in a conundrum! lol.gif

 

Inquiring minds want to know, wink.gif

Maybe it was Carl Zeiss ring finger size...any guess is as good as others!


Edited by GalaxyPiper, 09 February 2020 - 12:04 AM.

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#13 Ben H

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Posted 09 February 2020 - 12:33 AM

Even more information, including on various other diameters used in antique and vintage scopes from a thread in 2012

 

https://www.cloudyni...e-size-history/

 

The most logical, practical explanation being that 25mm tubes were a standard size, and 24.5mm eyepieces would fit in 25mm tubes. 


Edited by Ben H, 09 February 2020 - 12:36 AM.

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#14 Kasmos

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Posted 09 February 2020 - 03:52 AM

Even more information, including on various other diameters used in antique and vintage scopes from a thread in 2012

 

https://www.cloudyni...e-size-history/

 

The most logical, practical explanation being that 25mm tubes were a standard size, and 24.5mm eyepieces would fit in 25mm tubes. 

I wondered about that Sat. evening, which made me go measure the outside of an slip fit diagonal. It looked to be a little under an inch. Which made me think it might have to do with the diameter of a common available tubing to fashion into draw tubes, visual back, etc.


Edited by Kasmos, 09 February 2020 - 03:55 AM.

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#15 Astrojensen

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Posted 09 February 2020 - 04:25 AM

The most logical, practical explanation being that 25mm tubes were a standard size, and 24.5mm eyepieces would fit in 25mm tubes. 

Unfortunately, this explanation doesn't hold any water whatsoever, since eyepiece adapters on telescopes, diagonals, etc., where always elaborately machined from considerably larger stock. I've never seen an antique telescope, where this isn't the case.   

 

I'm afraid the origin of the 24.5mm eyepiece barrel is still a mystery. What we do know is that Zeiss is the earliest known user, but I'm speculating that maybe they actually got it from someone else. I can't figure out who, though. Fraunhofer/Merz seems a likely guess, but it could be someone else, too.

 

 

Clear skies!

Thomas, Denmark  


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#16 DAVIDG

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Posted 09 February 2020 - 11:26 AM

    I have seen "standards" like this before  that on their face value seem to be a mystery,  but when researched a bit deeper  the reason is usually from a simple reason, and usually it comes down to what was easily available at the time.

    Having done machining to make prototype equipment, you take what is easily available. Tubing is spec's out on the OD. So my guess is that this started because some manufacture could easily get 1" OD tubing which is 25..4mm. So if the wall thickness was 0.45mm the ID would be 25.4 - (2 x 0.45mm)  = 24.5mm  So the eyepieces are machined to fit that ID tubing. Once the standard is established then it is carried forward. So looking at other parts that are machined from heavier stock, may be giving the wrong impression has to why a simpler hypothesis maybe the reason. 

    Today we have a number of companies making telescopes and eyepieces. We choose certain brands over others.  The economics of selling eyepieces is that you make them to a standard that can be used by the most consumers since that means you have the largest market and can make the most money. So if you look at the 24.5mm standard, once it was established for whatever reason, it was held to because that is were the most profits could be made vs a non "standard" size.

 

 

              - Dave  


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#17 lonn

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Posted 09 February 2020 - 02:28 PM

Im with Dave on this one.



#18 Astrojensen

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Posted 09 February 2020 - 04:35 PM

    So if you look at the 24.5mm standard, once it was established for whatever reason, it was held to because that is were the most profits could be made vs a non "standard" size.

I'm not even sure the 24.5mm barrel diameter was considered any sort of standard before it was adopted by the Japanese. I know Zeiss used it as their own standard, but I don't know if any other German brands used it before WW2. I know Kosmos (supplied by first Merz, later by Wachter and Lichtenknecker) used 31mm diameter eyepieces (NOT 31.7mm/1.25"!) for a very long time, well into the 1970'ies, possibly later. They still list them in a catalogue from 1980. Steinheil used a propietary thread diameter and according to their 1907 catalogue, all their eyepieces for their own telescopes are thread-on only, although some of the eyepieces could be made with a push-fit barrel to fit the "popular size", but what size that is, is not specified!   

 

To summarize: We know that Zeiss used the 24.5mm barrel and that the Japanese adopted it, possibly before WW2, but certainly after, and it became popular once cheap Japanese scopes flooded the market.

 

Other than that, we know very little with any degree of certainty.

 

 

Clear skies!
Thomas, Denmark 


Edited by Astrojensen, 09 February 2020 - 04:40 PM.

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#19 GalaxyPiper

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Posted 09 February 2020 - 04:53 PM

I had read on an earlier thread that 25mm was a standard size for plumbing pipe. It's obvious that you can't make a 25mm eye piece to fit into it, so you would have to turn down the barrel of stock to make the eye piece fit, hence the 24.5mm or 0,965 inch standard.

Industry goes from a known to and unknown to save on re-inventing the wheel. I'm sure this was the practice even back then in the 1800's.

They didn't have modern cars either, they mounted crude engines onto established carriages.

Karl Benz invented the first auto car this way, and his wife Bertha promptly absconded with it, to drive 65 miles to her mother's house, stopping only at drug stores to get kerosene to keep the vehicle running.

She wanted to show it off.

belushi.gif https://en.wikipedia...iki/Bertha_Benz


Edited by GalaxyPiper, 09 February 2020 - 05:03 PM.

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#20 Dan /schechter

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Posted 09 February 2020 - 05:28 PM

I'm not even sure the 24.5mm barrel diameter was considered any sort of standard before it was adopted by the Japanese. I know Zeiss used it as their own standard, but I don't know if any other German brands used it before WW2. I know Kosmos (supplied by first Merz, later by Wachter and Lichtenknecker) used 31mm diameter eyepieces (NOT 31.7mm/1.25"!) for a very long time, well into the 1970'ies, possibly later. They still list them in a catalogue from 1980. Steinheil used a propietary thread diameter and according to their 1907 catalogue, all their eyepieces for their own telescopes are thread-on only, although some of the eyepieces could be made with a push-fit barrel to fit the "popular size", but what size that is, is not specified!   

 

To summarize: We know that Zeiss used the 24.5mm barrel and that the Japanese adopted it, possibly before WW2, but certainly after, and it became popular once cheap Japanese scopes flooded the market.

 

Other than that, we know very little with any degree of certainty.

 

 

Clear skies!
Thomas, Denmark 

Hello everyone,

 

I browsed thru this topic again this morning and thought I would throw a wrench into the subject.

This is what I understand about Zeiss and this subject:

Zeiss began its Astronomical department in 1894. The earliest, fairly complete Zeiss that I have seen pictures of has a serial number on the objective that is in the low 100"s and dates older than 1900. How much older I can only guess. It came with at least 12 eyepieces that appear to be standard .965"eyepieces. I cannot say for sure that Zeiss never made eyepieces with a barrel diameter less than .965", but I can say early on they made a lot of different focal length .965" eyepieces which may lead people to believe that they were the first company to do so.

 

Now here comes the  so-called "wrench in the subject":  I own a John A Brashear 8" reflector that has a metal tag on it that says John A. Brashear, Allegheny, Pa.   #32.  Since Brashear moved into its Allegheny factory in 1886, I am making an assumption that my #32 reflector most likely dates pre 1890, several years prior to the establishment of Zeiss' Astronomical department. It came with three brass eyepieces, each which look like typical Brashear eyepieces. One has a barrel diameter of 1.29", indicative of very early Brashear eyepieces, and the other two have a barrel diameter of approximately .965".  I say approximately because I have never directly measured their diameter. However, my .965"Zeiss eyepieces slip into the custom adaptor like they were made for it.

 

Could Brashear have been the first to use the .965" standard or did he copy it from another manufacturer? I do not know.

 

My Brashear 4" refractor alt/az mount shares a couple of similarities with Zeiss. The design of the trunnion clamps are very similar to Zeiss. That mount even has a rubber bumper to prevent the tube from denting if it is allowed to crash into the mount if the user lets go of it as he is changing eyepieces or accessories. My Zeiss Travelers have the same bumper as does the alt/az mount that came with the 80 A Zeiss refractor, dating approximately 1909, I acquired in Spring, 2019. Who designed the trunnion clamp and/or bumpers first? I do not know, but it is apparent that Brashear was aware of Zeiss and Zeiss was aware of Brashear designs. All of this is wonderful food for thought.

 

Hope you all enjoyed my "2 cents" and enjoy the Oscars tonight.,

Dan


Edited by Dan /schechter, 09 February 2020 - 07:36 PM.

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#21 clamchip

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Posted 09 February 2020 - 06:41 PM

It's interesting my pre war B&L refractor has a odd size, 1.1 inch, and yet B&L and Zeiss

were sort of partners at the time (the Triple Alliance).

The .965" is great for the popular turret eyepiece holders of the vintage era.

The 1.25" may have become popular here in the US with the ATM movement because of

this size is easily made and adapted from standard plumbing supplies.

 

Robert


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#22 DAVIDG

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Posted 09 February 2020 - 06:50 PM

 One of the other reason why Japanese telescope followed the Zeiss standard is that after WWII, the US was helping to rebuild Japanese economy and brought Zeiss into the teach the Japanese  mass production techniques for optics  So it makes sense that they would adopt the Zeiss standards.

     I just had another examples of this. A friend purchased a small Takahashi mount that was made in the early 80's off on Ebay. I made a new hand paddle to  replace the missing one to the control the electronics in the RA motor housing. He went to put the mount on a tripod and discovered that the threads for the tripod mount is a Whitworth type !  Whitworth is a British standard on a Japanese mount ? It is most likely left over from 35 years earlier. 

 

                  - Dave


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#23 ccwemyss

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Posted 09 February 2020 - 07:09 PM

Now here comes the  so-called "wrench in the subject":  I own a John A Brashear 8" reflector that has a metal tag on it that says John A. Brashear, Allegheny, Pa.   #32.  Since Brashear moved into its Allegheny factory in 1896, I am making an assumption that my #32 reflector most likely dates pre 1890, several years prior to the establishment of Zeiss' Astronomical department. 

Sorry, I'm not understanding this. If they moved to Alleghany in 1896, how would it be earlier than 1890? Or should that be 1886?

 

Chip W. 



#24 Jon Isaacs

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Posted 09 February 2020 - 07:32 PM

I am skeptical of the focuser tubing idea.  My thinking:

 

By the 1890s, Germany would have been standardized on metric system so 25.0mm tubing have been standard.  A 24.5 mm ID would mean a wall thickness of 0.25mm. That's 0.010". That's very thin, about the thickness of the pop open lid on a can of cat food.

 

Even if they started with 1 inch tubing the wall would be 0.45mm = 0.018". Still very thin. 

 

For comparison, a 1.25 inch eyepiece has wall thickness of about 1.9 mm = 0.074 ".

 

Writing this, what does make sense to me is this:

 

Modern tubing can be very round, DOM, drawn on a mandrel maybe +/- 0.001 ".  Even then it can be out of round. In the 1890's, it probably was not as good as what we have today. But

 

But even today, if you start with a 25mm OD tube and want to make a batch of eyepiece barrels, the first thing you do is put them in a lathe and clean them up so they're straight and round. Taking 0.5 mm off the OD would pretty much guarantee you that all the tubing would clean up, I'd spec something like that. 

 

From my perspective as an engineer, this fits very nicely, it fits the metric system, it explains why it's 24.5 mm and not 25.0 mm.

 

Jon


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#25 Dan /schechter

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Posted 09 February 2020 - 07:36 PM

Sorry, I'm not understanding this. If they moved to Alleghany in 1896, how would it be earlier than 1890? Or should that be 1886?

 

Chip W. 

Good catch Chip. Brashear moved to Allegheny in 1886.

Dan


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