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I’ve built two built optical instruments from scratch. One was a BVRI two channel chopping photometer and the other (in collaboration with Dr. John Stein who is now at Geneva College) was a three channel astrometric photometer.  I used the photometer and astrometric photometer in the early 1990's while working on the classification of narrow-field astrometric reference stars and  testing the precision of astrometric measurements for interplanetary spaceflight. The 2-channel photometer resided at the SARA Observatory, but was removed when SARA acquired a CCD camera. Since the camera met the photometric needs of the SARAns, the photometer was retired.

The photo above shows the photometer on the back of the SARA 0.9-m telescope.  The two photomultipler tube housings are the silver boxes seen pointing to the upper left and lower left of the image. Starlight focused on the photometer’s diaphragm is beam-split to two PMTS.  Before reaching the photocathodes, the light traveled through selected UBVRI filters in front of each tube, as well as separate fabry lenses.  The idea was to make color measurements, which are possible even in weather which is not entirely photometric (e.g. high cirrus).  Clouds are grey.  The photometer was intended for color-color measurements of astrometric reference stars used in the Allegheny Observatory narrow field astromteric program.

The photometer is retired.

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