Re: ATM RE: Making a Schmidt-Cassegrain

[Bill Marriott <btk@pacbell.net>]

Re: Making and getting glass for a MakNewt

1) For the corrector, you should use Bk-7 which can be purchased in slab
form from 1) United Lens 508-765-5421 They have a $75 min. order, you
may want to get your primary blank from them also.

2) Ohara, SBL7 I believe is there Bk-7 equivilent 714-858-5700
   This is of Japaneese manufacturing, and is very good glass

3) Newport: don't have their number, they are on the web, may have round
blanks, but are not consistant in their deliveries......8+)


 Order it thick, as the material is soft, stock comes off like butter,
especially with rough grits, and you may find your self doing a lot of
extra grinding as you fine tune the ROCs of the corrector. I have a OSLO
file on my 6" f8.5, which you can scale to a larger size. I believe you
can drop down to f6 and still have outstanding raytracing specs, below
that, its a matter of what is acceptable to you.

Regards

Bill Marriott
btk@pacbell.net
http://www.starlightoptical.com