Re: [ATM] Mike lockwood's flats page

[steve beccue <lsteve@Beccue.com>]

The light sources/filters used here are perhaps somewhat difficult
to locate.  Are LEDs (or subthreshold lasers) to broad a source
for this?

Steve Beccue
steve@beccue.com

On Mon, 7 Mar 2005, Mike Lockwood wrote:

> 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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