MAKER: JOSEPH ZENTMAYER

MODEL: 'GRAND AMERICAN'

c. 1865

SIGNED:J.Zentmayer, Maker, Philad' ^a  

SERIAL NUMBER: 291

This page is devoted to Zentmayer's Goniometer Stage with gliding slide holder. It was invented about 1860 and widely copied in variations throughout the world.

These images show the stage without the gliding slide holder and then with it in place. Note the very slightly elevated bars that the slide holder rides on.

Shown here is the glider component, top and bottom. Note the that bottom surface is about 1/3 glass. This same glass plate is the glass that shows through the top 'window' and against which the tension screw rests.

Note the ivory-tipped tension screw.

Note the silver-scale calibration for stage rotation, and the piece of glass dovetail-fitted to the bottom of the slide holder.

The rotation of the stage is accomplished in a precise fashion by the use of concentric rings. There are actually four rings with two overlapping the ones on top of them to preventing the stage from coming out. Centering the optical axis is accomlished by adjusting the three adjusting screws protruding out at 120 degree intervals around the ring supporting the stage. One of the three is visible in the photograph.