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RE: Testing An Hyperboloid Convex

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Posted by Robert May on June 23, 2000 17:16:20 UTC

Been working on how to do the Hindle Test and have found out some interesting stuff. First off, it seems to be rarely done by those outside of a few places because of the need for testing optics. Second, the test really is pretty easy to setup (compared to making an interfrometer and setting it up) if you measure things right.
Here`s how it is setup. You need to know the ROC of the Hindle sphere and the two focii of the secondary under test. The secondary is placed so that it`s near focus (the one to the back of the mirror) is at the Center Of Curvature of the Hindle sphere and everything is squared up so that the Hindle sphere is equally reflected in the secondary (getting the two points actually in line with each other) in the way that you would normally do a collimation of a Cass. You then measure from the surface of the secondary out back of the Hindle sphere (hopefully you have chosen a sphere that will allow this) and this is where you test for a spherical null. If the hyperbolic curve is off, you will end up moving the tester in or out and this is the second focus for producing the Schwartzrchild Constant for the surface. If the test shows anything but focus error (secondary doesn`t evenly dim across but rather has zonal errors) you need to do more figuring to correct the problem.
I hope that you understand what`s going on from this description.

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