Free and Open to the Public

2 mini-talks

Yerkes Observatory 
The beginning of the “Big Eyes in the Sky” for George Ellery Hale and me 
By Cale Shipman

The 40 inch refractor is the largest and last Alvan Clark telescope ever build. It is housed in an observatory that can only be described as a national treasure. Located near Lake Geneva, Wisconsin and currently under threat of destruction.

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Refiguring the Patterson 14.5” Mirror 
By Robert Horton

In this mini-talk we will explore the techniques that were used to refigure a medium sized Newtonian telescope mirror using both traditional Foucault testing as well as the latest advances in amateur interferometric analysis. First, we will walk through the various means by which we can measure the mirror to compare it to the desired shape and then we will see how to utilize that information to drive the refiguring steps needed to bring the mirror to that goal.

Example instruments of both a Foucault tester and a Bath interferometer will be shown and the process through which their measurements are made will be demonstrated and the pros and cons of each method will be explained. In the end, the precise shape of the mirror will be known and the expected performance can be simulated. Hopefully, when the mirror is installed at the HOS (aka GMO) sometime this spring, the actual performance will match these simulations.