Re: [ATM] A model of the Hindle Sphere test of a convex Hyperboloid

[Jim Burrows <burrjaw@earthlink.net>]

At 2005-03-31 14:14 -0500, James Lerch wrote:

>It would appear that the spacing between the
>concave sphere and the convex hyperboloid are impressively sensitive to a 
>change
>in distance.  If I modeled it correctly, it would appear I have to get the
>spacing between the two mirrors to within +/- 0.01mm (how exactly would I
>accomplish that?)

Get a dial caliper - they usually have a little rod that moves out of the 
other end of the handle from the caliper so that you can do inside 
measurements.  The one I have says .001" which isn't quite as good as your 
requirement, but I think if you run the Hindle test non-null (see later), 
the requirement eases a little.

>I am starting to come to the conclusion the Hindle sphere test may be near
>impossible to implement with quantifiable results, however I hope I'm 
>overlooking some rather obvious fact
>in my blissful ignorance.. :)

On my first 10" RC cass figuring, I ran a Foucault test on the Hindle + 
secondary, putting the mask on the Hindle sphere.  Back then, I didn't know 
about the slitless Foucault version, so I used a beamsplitter and matched 
the returns at the focus using ground glass and a microscope.  The test 
reduction has to take account of the light 
path:  source-secondary-sphere-secondary-KE.

Unfortunately, I used HCF and both surfaces were too rough, so it's back to 
the pitch lap.  I'm using webcam Hartmann for current primary testing; when 
it gets good enough, I'm going to program up a version of 2D Hartmann for 
non-null Hindle testing (if it can be done).

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84) 

_______________________________________________
ATM mailing list http://www.atmlist.net/