Sensitive spectroscopic instrumentation is now sufficiently portable to be used in field experiments involving terrestrial light sources as well as for astronomical observations. We report the results of a 20 night investigation of a phenomenon known as “Marfa lights” with the aid of a Schmidt-Cassegrain telescope and a CCD-array spectrometer. We show that the combination of computer azimuth and altitude logging, video recording, and continuous spectroscopy provides enough data for unequivocal identification of false positives such as distant streetlamps, automotive headlamps, and fires. We demonstrate that spectroscopic analysis of atmospheric molecular oxygen absorption can be used to determine distances of continuum-spectrum sources with an accuracy of 6% or better for distances of 4 km or greater. We also used astronomical objects for both directional references and approximate estimation of the system noise level in terms of minimum usable light flux.
Spectroscopy applied to observations of terrestrial light sources of uncertain origin
Karl D. Stephan, Sagar Ghimire, William A. Stapleton, James Bunnell; Spectroscopy applied to observations of terrestrial light sources of uncertain origin. Am. J. Phys. 1 August 2009; 77 (8): 697–703. https://doi.org/10.1119/1.3130609
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