An Automatic Continuum Compensating Photometer for Observations of Aurora and Airglow

An auroral-airglow photometer is described which automatically samples the night sky continuum at a wavelength adjacent to the emission line and subtracts the contribution of the continuum to the total observed signal. The sampling rate of 150 cps permits the subtraction of fluctuations in the continuum. Emission intensities over seven orders of magnitude may be monitored in unattended operation with an over-all response time of 1 sec/decade. Three emission wavelengths are monitored sequentially. The logarithm of the intensity is automatically recorded on a strip chart recorder. Full-scale deflection of the recorder pen corresponds to one decade of light intensity.