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greenglass
professor emeritus
Reged: 01/22/06
Posts: 540
Loc: Ontario, Canada
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This is what I had in my 5" dob, 1 fringe or 1/2 wave surface.
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10" f/5 dob unf.
7x50 Tasco binos
Edited by greenglass (07/09/09 03:36 PM)
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greenglass
professor emeritus
Reged: 01/22/06
Posts: 540
Loc: Ontario, Canada
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Same one another direction, well now I know it's a bad one.
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10" f/5 dob unf.
7x50 Tasco binos
Edited by greenglass (07/09/09 03:34 PM)
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1413
Loc: Sin-sin-atti
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Quote:
1 fringe or 1/2 wave surface
I agree it looks like 1 fringe but it would be 1/2 wave in air only. Under water however 1 fringe is only 3/8 wave because the wavelength in water is shorter than in air. It's a more sensitive test in water.
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Ed Jones
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greenglass
professor emeritus
Reged: 01/22/06
Posts: 540
Loc: Ontario, Canada
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2.25" minor axis seems flat
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10" f/5 dob unf.
7x50 Tasco binos
Edited by greenglass (07/11/09 01:14 AM)
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1413
Loc: Sin-sin-atti
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I think you're right but the contrast is a bit low. Can you elaborate on how you did it? How difficult is it for you to do?
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Ed Jones
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greenglass
professor emeritus
Reged: 01/22/06
Posts: 540
Loc: Ontario, Canada
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I used the water Rayleigh tester I made last week, I took about 20 pictures and took an hour to find the fringes and used red and green food color cause it has an old silver coating that's 1/2 gone. Sometimes it takes over an hour to find the fringes, or rarely a couple minutes, mostly about 20 minutes, the pictures came out very yellow for some reason, that's why the contrast is poor. Also I noticed the water moves and gives false readings, my dog walking upstairs shakes the water a couple fringes and I'm on a cement basement, window closed, back about 2 feet from the tester so I don't breathe on it, and don't move around in the chair and wait 10 seconds and take a picture. Still some pictures show bent fringes which bend another direction in the next photo without touching anything. But most are simular.
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10" f/5 dob unf.
7x50 Tasco binos
Edited by greenglass (07/11/09 08:57 PM)
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 652
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stoped by ed/s and he showed me the water test /ed makes it easy .cool test
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greenglass
professor emeritus
Reged: 01/22/06
Posts: 540
Loc: Ontario, Canada
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I found a neon night light at dollarama
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10" f/5 dob unf.
7x50 Tasco binos
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1413
Loc: Sin-sin-atti
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If you use food coloring or better yet a cerium mixture try to get the reflection from the aluminized flat equal in brightness to the reflection off the water surface. If you do that before you bring the 2 laser dots together the fringes will be very easy to see.
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Ed Jones
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