[meteorite-list] polarizers

From: STARSANDSCOPES at aol.com <STARSANDSCOPES_at_meteoritecentral.com>
Date: Sun, 23 Sep 2007 11:57:18 EDT
Message-ID: <d35.14ddb6bf.3427e6de_at_aol.com>

In a message dated 9/23/2007 6:56:09 A.M. Mountain Daylight Time,
marcin at polandmet.com writes:
Hi Tom.
I just read Your january article about polarizers.
But I dont understand how You can see chondruls through surface ?
Your photos are incredible, but I can't imagine how You do that without
polishing surface to remove polished surface (polished by sand).

When I look into stone through one polarizers nothing happend, when I get
two then nothing happend, only screen become darker when I rotate it. So how
did You do that :)

My polirize filters are nice for most of TS, but maybe there are better ?
Any suggestions ?



Glad you asked!

Hi Marcin and list members, If the whole image is getting darker when the
polarizers are rotated then they are not positioned correctly.

Always remember:

One filter between the light source and the sample.

One filter between the sample and the microscope objective (or your eye if
no microscope is used).

This concept applies to both transmitted (pass through) and incident
(reflected) light.

Only transmitted Xpol produces the vivid colors associated with Xpol
examination.


In answer to Marcin's question. Those rocks were examined as shown in the
first picture with no prep work. The samples were imaged as you see them!
The results are so important in examining an uncut sample, I don't understand
why every one who collects meteorites does not have a cross polarized light
set up.

Marcin's other question about what polarizers to use. On my Neophot I use a
Glan-Thompson style that produces almost total extinction. These polarizers
are expensive and bulky, you don't need those at nearly $500 each (and it's
X2). I don't however, like the films. The ones I have tried distort the
viewing with an irregular film surface. Particularly avoid the adhesive backed
films as they are the worst for distortion,

I like glass camera filters. What ever style works fine. Circular is my
first pick. These are cheap used almost any where. Even eBay can be a cheap
source. Quality glass camera filters to not disrupt the image and the metal
frame often allows for rotation. About half the filters I pick up rotate in
their holder.

Garage sales and thrift stores are my first hunting grounds and I bought
tons (translate: a lot!) at $1 or less. Yep $1 was my cut off. Except for a
huge 150mm monster I paid $5 for. I haven't found a use for it but I bought it
because it was cool.

One further note. If you have a rock saw, the class filters cut just fine.
I have cut custom sizes to fit inside microscopes and make for a near OEM
application.

If you are going to my Gallery, please look at the Juvinas Eucrite Xpol thin
 section micrographs.
http://www.meteorite.com/meteorite-gallery/Micro_Visions.htm

Jeff Hodges owns the thin section. It was polished to 1/4 micron on both
sides. This is a big deal as generally thin sections do not have a very high
polish, as it is not necessary to identify minerals and structure. I am
using an aus Jena Aplanatic Pancratic Condenser. This allows me to focus the
incoming light exactly on the thin section and then focus the objective. The
results are stunning.

Please take a look and let me know what you think. You will be amazed.
Don't just say you have seen plenty of Xpol shots before "What makes Tom's so
special?" LOOK, it will be worth your time.

Thanks, Tom




************************************** See what's new at http://www.aol.com
Received on Sun 23 Sep 2007 11:57:18 AM PDT