Re: ATM very fast dob (f/D<4)

[Aplanatic@aol.com]

Hi Mel:

> I wonder how you would feel if you released your 4 element corrector
>  design to the atm list.  A number of us are wishing to get into 1M+
>  optics and getting past the f/3.5 barrier is becoming more of an issue.

Yes, those huge ladders really scare me. <g> (No kidding, someone is going to 
break a neck someday.)
  
>  Also, can you say where you got your cell blank from?

Well, it's not my project per se.  I am involved with a little mirror and 
telescope making class at El Camino College here in LA, and the professor 
that runs the class (Perry Hacking) and several collaborators have purchased 
a pre-formed blank from some fellow in Az.  

I have volunteered my time as a glass pusher towards the cause, anticipating 
that I will learn a lot about making large fast paraboloids in exchange for 
my time.  Anyway, pushing glass is more fun than a session at the gym and 
probably a better work out.

I will find out for you who is making the blank and what it cost.  In 
addition, I will ask if the coma corrector design can be published at large.  
I would think so.

I know that the quote for the four-element coma corrector (from a local 
optical shop) was high (it is quite large in diameter).  The shop will need 
to make the tooling for the eight surfaces involved.  In fact, because of the 
tooling cost, it so turns out that 8 or 10 sets of corrector lenses is not 
too much more money than one set, and Perry is thinking that it may be 
possible to sell the other sets to other ATMs, at cost.  They still won't be 
cheap, however.

Dave Rowe
Torrance, CA