Re: ATM: Large obstruction Newtonians

[Anthony Stillman <atmer@flash.net>]

Paul,

If its not worth doing, there are still two collections of people who will.
ATMs and goverments.  The US goverment has made (well technically,
specified) a several large obstruction instruments.  Of those with which I
am familiar, tube length was the defining issue.

There are several designs which are of interest.  Not too long ago there
was a thread on the (a) Couder design.  This design may have an obstruction
as large as 70% of the primary (more typically 50%)  A link to a couple of
.pdf files of papers by Willstrop was posted in that thread.  A
configuration similar to Couder's was described by Schwarzchild in 1905.

Regarding removing central portions.  Rick Blakley wrote a paper describing
what he called a "cesarean".  The figure of the primary was such that the
central portion of the mirror could be removed and then used "as is" as the
secondary.  I spent some time today looking for that article.  I didn't
find it.  I remember putting it aside to re-read.  Those who know me, know
what this means.  When I find it, I'll post the reference.

Anthony