[meteorite-list] NWA 5000 micrograph techniques

[STARSANDSCOPES at aol.com]

NWA 5000 micrograph techniques
 
Hi list,  I am sure many of you are not interested in the techniques I  used 
to produce the NWA 5000 micrographs but I have had quite a few emails (and  
not all from microscope users) so I thought I would address what was unique to  
this material.

The solar wind Vesicles are found in the glass and the  trouble with this 
glass is it is nearly completely isotropic.  What that  means is, when you use 
cross polarized light, the glass is black and these black  dots (Vesicles) 
against a black back ground are hidden.  So in standard  full Xpol, they would be 
easy to miss.  

Bright Field reveals little  more and no color!

Additionally, when a wave plates is applied   the back ground color drowns 
out the photo.  

A measure of just how  isotropic this glass is, is nicely shown in the fifth 
image of today's Rock From  Space Picture of the Day.  Birefringence in the 
glass would be visible by a  shift in color!  And when you look at the photo 
with this in mind, you can  see there is not much color change going on in the 
glass when compared to a  clear pocket.

I settled on polarizers at 45 degree with the addition of a  PS3 (see this 
months Micro Vision) quarter wave plate at full extinction.   Slight nudges of 
the wave plate off of full extinction draws out some color in  the birefringent 
material, making the photo more pleasant with out tinting the  glass.

My Meteorite Times Micro Vision article is on the PS3 quarter wave  plate.  
You should check it out if you are interested in this stuff.   
http://www.meteorite-times.com/meteorite_frame.htm

Tom Phillips
 



**************It's Tax Time! Get tips, forms and advice on AOL Money & 
Finance.      (http://money.aol.com/tax?NCID=aolcmp00300000002850)