6 replies to this topic

[rmorein]

In other words, is chromatic aberration of these scopes determined solely by the aperture and focal length?

 

Or where there variations, with some glass makers offering slightly better dispersion characteristics?

 

Or to put it another way, are various reports of better than expected, slight chromatic aberration merely subjective, or from inexperience?

 

I'm not asking about the precision of manufacture, which would show up in other ways, such as a bad Airy disk.

[Sean Cunneen]

I think all were the Fraunhofer type. There are some European examples of Steinheil and American glass using the Baker design(Brandons) but narrowing down to your qualifications of 70's Japanese glass, I would say all are of the Fraunhofer type until you get to the Flourite objectives in the 80's. 

[jragsdale]

Goto had several Steinheil contact doublets, I have the 60mm f/20 version.

Attached Thumbnails

• 

Edited by jragsdale, 08 January 2025 - 04:38 PM.

[starman876]

Goto had several Steinheil contact doublets, I have the 60mm f/20 version.

How many suppliers of glass were there in Japan.   I bet each supplier was a little different in their composition of the crown and flint.  Might have been different evolutions of the glass makers and maybe the better scopes got the more exotic glass.  

[jragsdale]

How many suppliers of glass were there in Japan.   I bet each supplier was a little different in their composition of the crown and flint.  Might have been different evolutions of the glass makers and maybe the better scopes got the more exotic glass.  

From this post, sounds like Goto was an exclusive user of this glasss type.

Attached Thumbnails

• 

[starman876]

From this post, sounds like Goto was an exclusive user of this glasss type.

There you go.  You it the nail on the head.   I bet this was not the only lens with special glass in it.  Bet the special glass was more expensive so not every scope maker used special glass. Also, explains why there was such a wide range of quality when it came to the optics.   I know guys here did not take long to know whose lenses were special.

[PawPaw]

Goto had several Steinheil contact doublets, I have the 60mm f/20 version.

With regards to the patent document you posted the "Utility model"  that used blue plate glass is not a Steinheil design.  As stew referenced in his post this is a unique design used for their school models.   Goto finally ran out of blue plate glass and switched to a clear crown but kept the same optical design.   The utility model used in school telescopes survived until the late 1980's in their ST-5 and ST-6 models.  Goto used the "blue plate glass"  not because it was had any advantages over clear crown but simply it was available and inexpensive.  

 

Goto did use a steinheil design in their 80mm  models from the Mark-X era.  See: https://www.cloudyni...-for-1976-r3393

 

To answer the OP's question.....No. 

 

Dave Trott has an excellent video delving into early Tak designs and he also notes that Nikon and Goto were early users of low dispersion glass.  Nikon used their own proprietary glass.  Goto used Ohara during their early development.    https://www.youtube....h?v=v1jbt6jU-QY

Edited by PawPaw, 09 January 2025 - 09:41 AM.