Sensitive stellar photometer with a cassegrainian optical system for use in the 1300-2000-a region.

A sensitive photoelectric photometer designed for astronomical measurements of early type stars in the 1300-2000-A region is described. The photometer, which uses a wide aperture Cassegrainian optical system, has produced over ninety-four stellar observations with a limiting magnitude of mnu = 6.5. A number of methods of wavelength isolation have been used and are described, together with details of the method of absolute calibration of the instrument.