Absolute flux measurements in the rocket ultraviolet

A two-channel spectrometer was calibrated in the wavelength region 1200-3400 A and flown on an Aerobee rocket to observe the stars alpha Lyr, eta UMa, and zeta Oph. Standard tungsten lamps provided the absolute calibration down to 2250 A, and a photodiode calibrated by the National Bureau of Standards was the reference at shorter wavelengths. The molecular branching-ratio technique of relative calibration using the gases CO, NO, and N2 was a check on the absolute calibration. The flux from eta UMa agrees with the prediction of a hydrogen line blanketed model atmosphere within 10% between 1700 and 3400 A and within 4% over most of this wavelength region.