Re: [ATM] convex secondary

[Mike Lockwood <melockwo@uiuc.edu>]

Guy,

Guy Brandenburg wrote:
> 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.

As you mentioned in your later email, for the compact fluorescents, in 
fact the green emission is in two lines, fairly close together.  This 
produced much poorer fringe contrast than the red line.  The red works 
surprisingly well, and is easy and cheap to build (3 compact 
fluorescents for $12, one piece of Ruby Red 1/8" thick plexiglass).

Now I use bulbs with a single green line.  I have been told that these 
bulbs are the same type as are used in Edmunds Industrial Optics $320 
monochromatic source.  They have a very strong green line, and a 
purple line.  They are small black lights without blue filters.

The bulb is a F8T5BL:
    F8 = 8 Watt, T5 = 5/8" diameter, BL = black light

DON'T get F8T5BLB - BLB = black light blue.

So, for the cost of two fixtures ($10 each) and two bulbs ($4 apiece) 
and one sheet of filter material ($6), a total cost of $34, I've got a 
great monochromatic source that's the same brightness as (16 W) as 
Edmunds source, which costs $320 plus shipping!

I could use a better diffuser.  The ground glass (ground by me with 
320 grit on both sides) is not quite enough, but I want to avoid 
cutting down on the brightness.

	Mike Lockwood




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