From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


All you need to test a flat is another transparent flat.  If the flat under
test is aluminized, you will still see the fringes but they will be a fair
bit fainter than an uncoated flat will be.  The light source wants to be a
narrow line source rather than a broad source although a floursecent light
will work on two uncoated flats.  A neon bulb will do fairly well as the
orange is fairly decent for being a line.  Some of the power strips use a
neon bulb for the illumination of the power switch and a good bright one
will work.
Place the two flats in contact after cleaning them throughly (dust will
keep them apart as well as oil films) and let them dry for a moment (the
water film also keeps them apart) before putting them together.  You should
see black and light color lines shortly after you put them together and the
lines will be faint but there.  Needless to say, the work should be done in
a darkened room with the illumination source the only source of light. I've
been quite successful showing fringes to people under the blue-white
floursecent lights and the fringes there are blue/violet in color with
edgings of the violet color.  Bouncing the light off of the surfaces and
then into your eyes is what really produces the fringes. Good luck!
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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