The Allegheny Observatory Trigonometric Parallax Program. The hallmark of the astrometric program at the Allegheny Observatory is high precision, approximately 0.001 arcsecond per parallax. Combining the Multichannel Astrometric Photometer and the new optical system of the Thaw refractor, the program has sufficient precision to obtain reliable trigonometric distances of several open star clusters as well as other luminosity standards in most parts of the Hertsprung-Russell diagram. Combined with data from a 70 year baseline photographic plate collection, the MAP/Thaw system has sufficient precision to define portions of the mass luminosity relationship previously outside of the domain of trigonometric techniques, and to make significant improvements in our understanding of the effects of age and chemical composition on the energy output of stars.
