Re: ATM Tiny lenses - cass sec - Endemann

["PETER JOHN SMITH" <pjifl@bigpond.com>]

I have been asked to give data on a 6 inch F:4 Endemann type scope.  It may
as well go into the archives for anyone else interested.

This should  be read in conjunction with the last post on the 8 inch F:4 as
some data and thoughts are not repeated but is relevant to both posts.

The diameter of sec is for a 30 mm diam field although changes little when
field id reduced.
The RC on back is for back testing so a hyperbola is formed on 6mm thick
BK7 secondary blanks

RCsec..F:NO..PV....conic..Diam...RConBack

200.......28.....0.40...-1.754....26...1494 convex
150.......37.....0.31...-1.524....20...1909 convex
100.......56.....0.21...-1.324....15...3430 convex
75.........74.....0.16...-1.234....10...8137 convex
50.......110.....0.10...-1.150......7..26380CONCAVE

It is interesting to see the amount of conic introduced by back testing a
plano convex lens which would be readily available.  6 mm thick BK7  .

RCsec....... back tested conic

300................-1.28
200................-1.27
150................-1.26
100................-1.23
75..................-1.21
50..................-1.16

It is obvious that a plano concave lens, tested and figured using a back
Foucault test would in some cases be almost perfect and probably in all
cases an improvement over a sphere.

A few graphs of some of this data would be good enough to interpolate for
different values.

Would be interesting figuring a 10 mm diam surface.  Would think one double
that size finally edged down considerably would be the way to go.  Probably
Very hard pitch for small lenses. Not easy but I would think with
experience and perserverance quite achievable. 

All the best
Peter Smith.