R. Egler

Peer Reviewed

Abstract: The plastic marine sextant has become a common sight in celestial navigation courses owing to its relatively low cost. Mixed statements concerning the quality of such sextants are heard; however, no experimental data seems to have been published concerning their accuracy. The temperature dependence of the index error is proposed as a first approximation indicator of the suitability of plastic sextants for navigation. This paper describes some experiments performed to actually quantify the change in index error with temperature, as well as examine the stability of the instruments’ index error at a constant temperature. These results were compared with the results of the same experiment performed on a metal sextant. While the changes in index error with temperature are much larger for the plastic sextants than for the metal sextant used for comparison, the changes were found to be highly linear and repeatable, and the index errors of the plastic sextants, when at a constant temperature, were as stable as the those of the metal sextant under the same conditions.
Published in: NAVIGATION: Journal of the Institute of Navigation, Volume 42, Number 3
Pages: 531 - 556
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