Re: [ATM] convex secondary

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

Mike,
I notice that you used the red wavelengths on those
compact fluorescent light bulbs in your monochromatic
light setup. Any particular reason why you used red
and not the green?
I have a similar setup, but I used some straight
fluorescent lights and filtered out all but the green
mercury line. 
(I think I need to add additional fluorescent lights;
only one is rather dim.)
I didn't like the compact fluorescenets because they
seemed to have two fringes very close to each other,
for easons I don't know.
Guy

--- Mike Lockwood <melockwo@uiuc.edu> wrote:

> Jonathan,
> 
> Jonathan Lavoie wrote:
> > Thanks Mike for this testing alternative.
> > Can you describe how the interference test is
> done?
> 
> Fringe testing lets you visually compare the shapes
> of two polished, 
> nearly-mating glass surfaces.
> 
> You put two clean, polished glass surfaces in close
> contact.  Only a 
> thin layer of air remains between them. 
> Monochromatic light is used 
> to illuminate the two pieces from above.  The light
> is reflected by 
> the two polished surfaces that are in close contact.
>  These two 
> reflected wavefronts constructively and
> destructively interfere, 
> forming "fringes".  That's the quick and dirty
> summary.
> 
> If you're interested, I (or others) can suggest
> links to better 
> descriptions.
> 
> > I guess the test plate has a concave shape
> identical to the convex wanted?
> 
> For the easiest testing, that's right.
> 
> > Where do you put the monochromatic light source
> and how can we get such 
> > light?
> > What do you look at when testing the mirror?
> 
> Here's a link to my testing setup:
> 
>
http://bi-staff.beckman.uiuc.edu/~melockwo/int_tester/int_tester.html
> 
> There are many simpler ways to do this, and my setup
> is modeled after 
> those depicted in various books.  I built this
> tester to be easy to 
> use in the long run (more than one mirror).  So far
> it's made four 
> mirrors - two Cassegrain secondaries and two flats.
> 
> The new page about flat testing (described in a
> message to the list 
> earlier this morning) has lots of photos taken with
> this test setup, 
> but with a new green light source.
> 
> Here's another very simple setup - just a laser
> pointer:
>    http://tlepage.home.mindspring.com/fringes.html
> 
> 	Mike Lockwood
> 
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> 


=====
Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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