Re: Stereo Microscope for Coin Collector?

sodaant@xxxxxxxxx writes:
I'm a coin collector and would like to buy a stereo microscope to
grade coins that I buy and sell.

What are some models to look at? What kind of magnification would I
need to see a full-field view of a U.S. silver dollar?

How big is a U.S. silver dollar? Not everyone lives in the USA, so many
people who read this will not know what field size you need. But
everyone knows how large a measurement like 1.5 inches or 40 mm is.

The maximum field size is often listed in manufacturer's literature. If
you don't have that, you may be able to calculate it:

The edge of the field is usually produced by a field stop in the
eyepieces. For a decent modern microscope with "wide field" eyepieces,
that stop is probably 20 or 22 mm diameter - the actual size may be
marked on the eyepieces after the power. The size of the field at the
subject is simply the eypiece stop diameter divided by the microscope
objective+body power.

For example, suppose you have a 7-40 X zoom microscope with eyepieces
marked "10X 22". If the eyepiece magnification is 10X, then the body
and objective magnification ranges from 0.7X to 4.0X. The eyepiece stop
is 22 mm diameter, so at the lowest power the field diameter is 22/0.7 =
31.4 mm.

Dave
.

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