Astronomical Optics/TASS Optics

["Merle W. Jephson-King" <mjking@wi.net>]

First of all, kudos to Elliot for his design.  This is exciting for 
him because he is trying something new.  The possibility of focusing 
different wavelengths has been around for years.  However, no one has 
done it in quite this way.

Now for a little history lesson.  The 36-inch refractor at Allegheny 
Observatory in Pittsburgh was designed for best focus for blue light 
which is the most sensitive region for photographic emulsions.  All 
other refractors in the world were designed to focus best for green 
light which is the most sensitive region for the human eye.  All of 
the refractors built around the turn of the century were glass 
doublets.

To do photometry you need to focus four colors for each filter 
wavelength.  At the same time, you need to perform respectable 
astrometry so you can identify the stars in the field.  The questions 
that must be answered are: "Is it cheaper to build 40 times 4 doublets 
for the different frequencies?" or "Is it cheaper to build 40 five- 
element units?"

Sending Requests For Quotation is a standard way of doing business and 
it lets you know; (1) whether your specification is feasible; (2) how 
much the program will cost; (3) how soon you might get it; and (4) 
sometimes things you never thought of.  Most of engineering done 
today is what I like to call "catalog engineering".  You think of a 
solution and then go search Thomas Register and all the catalogs you 
can get your hands on, to find out that your answer has been done 
before and all you have to do is find it and buy it.  

Are we trying to do "catalog engineering" or one-of-a-kind science?

Tom, we need to get together one of these Saturdays.  I have been 
weathering my first Wisconsin winter which has led to my prolonged 
silence.  I have a couple of basic concepts in mind for a focus 
mechanism depending on what needs to be moved.

Merle King