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 Post subject: proportion scope - which one and where to buy?
PostPosted: Sat Dec 07, 2013 4:13 am 
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I need to measure measure table width, crown height and pavilion depth, girdle thickness, crown angle and pavilion angle, and symmetry.

I need to find an old GIA proportionscope on ebay or get a:

http://www.szfable.com/e/products/Diamo ... scope.html I sent an email to them in regards to price and availability.
or
http://www.kruess.de/shop/Proportionsco ... ::115.html

No expensive machines.
Any insight or recomendations?

Thank you
Dennis


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 Post subject: Re: proportion scope - which one and where to buy?
PostPosted: Sat Dec 07, 2013 10:44 am 
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Hello,

There also at GIA store. It is more expensive: http://store.gia.edu/DLScope_Reticle_p/964300.htm

Brigitte


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 Post subject: Re: proportion scope - which one and where to buy?
PostPosted: Sat Dec 07, 2013 11:31 am 
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Sounds, interesting..... never used one. Has anyone?
What do you think the limitations would be for use in other scopes?


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 Post subject: Re: proportion scope - which one and where to buy?
PostPosted: Mon Dec 09, 2013 12:57 pm 
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It is probably very similar to the old Diamond Proportion reticle and will work in almost any microscope. You might want to pick up a stage micrometer to go with it to calibrate the magnification. (the GIA unit comes with one I think) You just have to make sure the ocular they sell it with is a 30 mm or 23.2 mm . It used to be 23.2 in the days of AO and B&L Gemolites and now is probably 30mm. Helps also to have an exactly matching , mating ocular so you can use it with both eyes open. But you could use it with one eye if you didn't want to buy the second ocular.

Of course the measurements would be more accurate if done on a Wild M400 or M series with the "S type" carrier since the convergence angle would be eliminated. This convergence angle also does not exist in the separate free standing Diamond Proportion Analyzers which like the aforementioned two scopes are square and plumb over the object of view. Hopefully somebody at GIA did an error calculation of the error and determined that it is not significant. The measurement could also be expected to be more accurate with a Common Main Objective type stereo versus a Greenough type for the same reasons.


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 Post subject: Re: proportion scope - which one and where to buy?
PostPosted: Tue Dec 10, 2013 1:27 am 
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Thank you all for your input. I am keep using visual estimates for table width and pavilion depth as well as crown angle. From there I use the math for other details.

I will keep working on getting info from Chinese proportion scope. I will post whatever I find out.

Thanks again

Dennis


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