4 replies to this topic

[Random2310]

I have become interested in Cassegrain telescopes recently and I was reading through Cassegrain Notes by Kenneth Novak. He mentions various Cassegrain designs and writes the following: 

 

 

The Buchreder-Cassegrain uses all spherical mirrors and a number of spherical refractor relay lenses.  The large five all spherical surfaces with the secondary discourage construction.

 

I could not find any information online about this design. I tried Google and Google Patent search.

 

By any chance, has anyone come across this Buchreder-Cassegrain design? Or know any additional information about it? I am really interested in seeing the light path for this thing.

Edited by Random2310, 13 February 2025 - 12:49 AM.

[RichA]

I have become interested in Cassegrain telescopes recently and I was reading through Cassegrain Notes by Kenneth Novak. He mentions various Cassegrain designs and writes the following: 

 

 

I could not find any information online about this design. I tried Google and Google Patent search.

 

By any chance, has anyone come across this Buchreder-Cassegrain design? Or know any additional information about it? I am really interested in seeing the light path for this thing.

http://jerome.xf.fre...=1&limitstart=6

[Random2310]

Thank you Rich! Novak made a spelling error. Its not "Buchreder", its "Buchroeder".

 

 

But it was especially Richard Buchroeder in the 68s who seems to have stabilized the concept of the relay telescope; Richard Buchroeder is a little-known American optician, yet he is the designer of a certain number of optics stamped... Meade. Originally, Buchroeder's telescope included a spherical primary and secondary and a seven-lens spherical aberration corrector relaying the focus. Buchroeder also imagined, which is clever, a Cassegrain telescope with variable geometry whose hyperbolic secondary could be replaced, depending on the use, by a spherical mirror and a relay... A year later, R Buchroeder modified and stabilized his concept by using a Mangin-type secondary compensating for spherical aberration, and thus reducing the complexity of the corrective relay but at the cost of chromasia: only four lenses were then used to relay the focus and correct this chromasia. Bushroeder nevertheless points out the critical nature of the concept, particularly with regard to the distances between mirrors and/or lenses.

[RichA]

https://www.cloudyni...tric-telescope/

[luxo II]

The idea of relay cassegrains was best covered by Don Dilworth - see for example section 11.2 of

https://www.telescop...eous_optics.htm

 

There are several variants of the relay lens configuration, they typically offer a very well corrected field. Depending on the details of the design there may be some capacity to vary the focal length (ie zoom) by shifting the elements.

 

See also https://www.slideser...pt-presentation

 

Don built a very elegant example which had no OTA - the secondary was supported on 3 legs extending from the central baffle -, it appeared in the ATM section of S&T.

 

https://www.cloudyni...-1534735879.jpg

Edited by luxo II, 14 February 2025 - 02:50 AM.