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 Post subject: AO Filar micrometer measurement oculars
PostPosted: Sun Mar 29, 2009 3:33 pm 
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Here are two auctions from the same seller that has been posting some good stuff on fleabay. Tim recently bought one of these made in Austria by Reichert of Vienna.(Not as well known as Zeiss and Leitz and Wild but every bit their equal in quality and innovation.)

These are filar eyepiece micrometers which allow you to make very accurate measurements through your microscope. It is my opinion that every gemologist should have these. You also should have a stage micrometer or a measuring reticle to calibrate them with. That is so you know how the measurement taken with this item corresponds to distance on the object stage.

It is a simple calibration and is done to essentially determine exact magnification. Then you can really specify sizes on , for example , small stones or facets accurately and easily.

These are for 23mm diameter oculars. If your scope has 30mm eyetubes you can get sleeves. It is VERY difficult, virtually impossible to find these in 30mm size.

When you look through this ocular you see about a ten millmeter scale. There is also a cross hair which moves across the field when you operate the micrometer. So you take the difference of two micrometer readings and that is the size in the eyepiece. You then divide that by the magnification which you have previously determined for that zoom setting, using your stage micrometer or measuring reticle or an accurate ruller.
Then you have the actual size of the item you are looking at , without resorting to plastic 0.1mm scales that are hard to read unless viewed through the scope too. And the measurements are likely to be much more accurate.


Here


and here.


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 Post subject:
PostPosted: Sun Mar 29, 2009 5:59 pm 
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DITTO

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 Post subject: RI measurements through your microscope.
PostPosted: Sun May 17, 2009 4:52 pm 
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The refractometer is the main instrument used to determine a gem's RI, but is it the only way to measure RI in faceted gemstones?
well, there is another way using these eyepiece micrometers and a regular micrometer to determine a gem's RI, i don't know why but this method is neglected and hardly ever used, maybe some of the Experts
here in this forum can explain why its neglected and hardly ever used.
:smt116


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PostPosted: Sun May 17, 2009 9:54 pm 
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Here
is a link to a thread on the the method of the duc du Chaulnes also known as the direct method.

Here too

It requires a micrometer to be mounted on your microscope. It does not require a filar or eyepiece micrometer. They are two different types.
The eyepiece micrometer is used to measure lengths of things that are magnified by the scope.


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 Post subject: the direct method
PostPosted: Mon May 18, 2009 7:17 pm 
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Thank you Gene, i was looking for more information about this method,
appreciate your assistance. :smt023


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