Re: [ATM] Mike lockwood's flats page

[Mike Lockwood <melockwo@uiuc.edu>]

Dave,

David Margrave wrote:
> thanks for posting those pictures.  I am also working on the
> three-disc flat method with 3 8" pyrex blanks.   I am going to set up
> a light box like you have done, with compact flourescent lights and
> red or green tint.  I got the red and green film from Tap Plastics,
> and also picked up some silver tint which seems to have one-way
> mirror-like properties, so I'm hoping i can just use that as my 45
> degree reflective surface to view the fringes.  I scrounged around for
> a while but couldn't find a low pressure sodium or mercury light.  I
> did find high pressure sodium at the big box stores and also a company
> called Kelsun distributors in Bellevue, WA.   Could you explain a bit
> more about your black light source?

Hope the plastic filters work for you.  I stumbled on the red 
plexiglass by chance, but it worked very well.

My current light source is composed of two black lights.  The bulb 
numbers are F8T5BL.  F8 = 8 watts.  T5 = dimeter, in 1/8ths of an 
inch, thus the diameter is 5/8".  BL = black light.  This is NOT BLB. 
  BLB = black light blue, which implies a blue filter is placed on the 
bulb.  This will knock out the green line, which is the one you want 
to use.

Other fluorescents also have a strong green line, and may work just as 
well or better.  A cheap spectrometer indicated that these bulbs were 
promising, so I used them.  They also consume little power.

> At this point I have my 3 blanks fine ground but not polished.  I am
> also working on an 8" f/8 spherical mirror which I will use for
> conducting the ritchey-common test on my candidate flats.  I suppose I
> am just making extra work for myself but I like to use more than one
> testing method.

Do as much spherometer work as you can to get them nice and flat.  The 
proper grinding sequence should make this happen anyway.  The 
spherical mirror will be useful and fun to experiment with.

	Mike Lockwood

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