Re: [ATM] A Null Test

[Ric Rokosz <radicell2@yahoo.com>]

> Ric Rokosz wrote:
> > >From my experience that isn't true.Have done a 24
> > incher f/3.3 and a 18 inch f/2.8 with a 6 inch
> custom
> > made lens I did and a 13 inch lens where I redid
> the
> > convex side.

Just to clarify a point,these lenses where not used in
combinatiion,as in one behind the other.Each was set
up alone in a pure Ross test.The 13 inch lens had a 94
inch focal lenght.


>         c) 25-25.4 mm diameter variable f.l. (c. 100
> to 200 mm) biconvex

I find your work on the these null lenses very
interesting and do appreciated the work involved.I do
have one concern and that is the use of biconvex
lenses.If one uses a vernier caliper to set the
spacing you need large jaws to reach down to the apex
of the lens and this can introduces angle error and
the resulted spacing error - not much of course but
how tolerant can the spacing be? Using plano-convex
lenses makes things a lot easier.

Ric


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