Re: ATM A Millies-LaCroix Diagram for Hyperboloids?

["Tom & Lou Krajci" <krajcit@3lefties.com>]

From: "Thomas O'Hara PhD" <thomasohara@yahoo.com>

>Can anyone suggest a method for modifying the Millies-LaCroix graphical
>representation of the Foucault Test for use on hyperboloids?

When I made my six inch, f/3.75 hyperboloid mirror for my astrograph, I
fiddled with the ML envelope, using the schwartzchild constant to adjust the
centerline of the envelope.  In my case the knife edge travel/ML centerline
was about 1.84 times that required for a paraboloid.  (Jim Burrows, I know
this is not exact, but for an astrograph it was good enough.)  I did not
know how to adjust the width of the tolerance envelope, so I just figured
this mirror until I considered it good enough.

That was my first mirror.  I thought it looked good under the various tests
I did:  foucalt, wire, and poor man's caustic.  Now that I use it, star test
it, and focus it...it's rough and zony...but still good enough for an
astrograph since overall correction is adequate.  Fast/hyperboloid mirrors
are tough to evaluate for overall smoothness and lack of zones...very deep
foucalt shadows.  Fortunately I made it easier on myself with my other
mirrors - long focus.

Tom Krajci