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Old Monday 18th September 2017, 15:56   #1
Binastro
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Hand made optics.

Are any of the objectives of top spotting scopes hand finished?
What about medium and lower priced scopes?

If hand finished, how many optical workers have the ability to hand finish objectives?
In which countries?
Are young technicians being trained to do this?

In Britain it is very difficult to find experienced optical technicians able to do this.
There are some.

Sony are proud of their new automatic machines that can aspherise fairly large optics to very high standards.
I don't know if this would be good enough for spotting scopes.

Are astro scope mirrors and refractors hand finished?
I suspect they must be.

A British master told me that of the 6,000 mirrors he had made only 3 did not need hand finishing.
Maybe automation has become so good that no hand finishing is needed?
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Old Monday 18th September 2017, 17:38   #2
jring
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Hi,

that is an interesting question. Given the fact that the allowable tolerances for lenses are quite a bit more relaxed in comparison to mirrors and also most designs work without aspheres, I would assume that most lenses are made more or less automatically like shown in here:

https://www.youtube.com/watch?v=OkWsk9rXpcU

https://www.youtube.com/watch?v=7T7BDeMU_Ks

https://www.youtube.com/watch?v=KpkAWZTwqI4

Very large and/or high quality astro scopes might get some hand retouching.

Even astronomic mirrors of quite acceptable quality (at least for smaller sizes, reasonable focal ratios and substrate thickness) are nowadays ground by machines in china - ask GSO how they manage this.

Very large, fast and/or thin mirrors of good quality are still the domain of a few artists, some of whom do some steps with machines but parabolizing is done manually there.

Joachim

Last edited by jring : Monday 18th September 2017 at 17:42.
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Old Monday 18th September 2017, 20:31   #3
Binastro
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Thanks.
I would think that even large Canon lenses are not up to the quality of a Swarovski 95mm unit.
Here I would think that the scopes could take 150x easily and possibly 200x visually.

Of perhaps a thousand camera lenses that I have tested visually only about 1% are or were of true astronomical quality. Usually mirror lenses, Dutch, Russian and U.S., but also some refracting lenses.

Even now lenses used for professional laser work need hand polishing because machine work is not smooth enough.

Are Takahashi refracting astro scopes hand finished?

My 1980s 20.5 inch f/3.9 thin mirror was hand made by one of the two top British optical workers at that time.
I was told about a year ago that it turned out to be 1/20th wave and I have no reason to doubt the maker's measurements.
I never got to use it to its full capabilities because of atmospheric conditions. But it was good.

I would think that the Pentax 100mm f/12 demonstrator was hand finished as were some other refractors.
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Old Monday 18th September 2017, 23:50   #4
jring
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Hi,

actually Canon-Optron is manufacturing the objective lenses for the fluorite Takahashi scopes (and most other companies using fluorite elements like Kowa, Vixen, Borg).

I don't know if they do hand finishing for those, but they are pretty good at it - the Zygo reports on the page linked below list figure P/V of 24nm - or 1/20th wave and surface roughness of 3nm - but on a lens...

http://www.canon-optron.co.jp/englis...te/finish.html

Joachim
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