Novembr 16-18—COLUMBIA, SOUTH CAROLINA: Annual show; The Columbia, SC Gem and Mineral Society; Fri. 10-6, Sat. 10-6, Sun. 12-5
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 Post subject: question about a refractometer
PostPosted: Fri Jun 29, 2018 8:54 pm 
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I picked up a cheap surplus refractometer off ebay and I checked a piece of amethyst and a peridot and both came up in range but I noticed when I move my head forward or up I get a shadow line about 1.69 that moves all the way down to 1.81 even without a stone.
This doesn't seem correct as the shadow would obscure the demarcation line if the ri were high enough.
Is this refractometer badly constructed and needs to be returned? or is this normal and I'm doing something wrong?

Thanks, Jim


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 Post subject: Re: question about a refractometer
PostPosted: Sat Jun 30, 2018 12:57 pm 
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Ok I think I got it, I inadvertently pulled out the ocular (press fit) and as I was going to put it back I noticed I could clearly see the scale to the bottom when the ocular was about 3/4 of an inch from the refractometer body.
I think I can fix this by making an adapter to move the ocular farther out.

Jim


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 Post subject: Re: question about a refractometer
PostPosted: Sat Jun 30, 2018 5:43 pm 
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Location: San Francisco
That's unusual, isn't it?


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 Post subject: Re: question about a refractometer
PostPosted: Fri Jul 06, 2018 4:42 pm 
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Barbra Voltaire wrote:
That's unusual, isn't it?


Probably not for this model, I think it is about as bottom of the barrel as you can get but it does seem to read accurately and it was cheap with light source, RI fluid and a removeable polarizing filter

The refractometer supposedly has a monochromatic filter inside, it came with a yellow led flashlight which makes the scale yellowish but if I use my xenon bulb flashlight the scale is bright white.

I thought the monochromatic filter would only show one color, I wonder if the disc inside is just a diffuser.

Weird though even with the eyepiece pull out as far as it will go the scale is blurry and I get a dark shadow over the bottom of the scale, If I bring it out not even 3/4" and angle it down slightly the scale is in focus and although there is still a shadow at the bottom it covers a smaller area and I can manage a reading if needed.

A discount from the seller for the problem and it works for me.

Jim


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