Calibrations of the airglow photometers and spectrometers

When observations of the same source are made by several instruments, the sources of apparent discrepancies in the results of these measurements are likely to be (1) differences in the operational definitions of the terms involved in the calibration procedure and (2) various sources of errors in the execution of the step wise procedure of calibrating the instrument. In this paper we discuss the major factors responsible for large errors such as the use of a low brightness source (LBS), bandwidths of the instruments, transmission characteristics of the optical interference filter, the effect of stray and scattered light by the instruments, as well as a step-wise procedure for minimizing the errors in a calibration of the instruments. In a test of these procedures the consideration of these factors resulted in minimizing the discrepancies in observations with photometers and spectrometers, yielding an accuracy of 20% or better in the measurements.