ATM RE: Tri-Space

[Roger Ceragioli <rogerc@as.arizona.edu>]

Hi, Steve and Ken and Others.

The main problem with Roland Christen's "Tri-space" (in my experience, 
at least) is the selection of Corning B58-53 glass.  Roland himself told 
me that his piece was fine.  But the piece that we got (as I recently 
mentioned) was awful.  You can't buy any directly from Corning unless 
you want to finance a whole melt of the stuff (about $40,000, I believe, 
for a few hundred pounds), but Glass Fab has a stock of it.  Apparently, 
what they have is "strip glass," i.e. a long narrow strip as supplied by 
Corning about 20 years ago.  The maximum width of it is about 3.75". 
 That sets strict design limits on the corrector.  But in any case, you 
may get a bum piece and it's not cheap:  our 3.75" dia. piece cost about 
$500.

So Roland's design is interesting, but in practice may well not be 
feasible.  A set of 3 disks of the raw glasses needed for our version 
cost $1700.  And it flopped.  

Take care,
Roger