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An Improved Oblateness for the Earth’s Thermosphere from Lunar Eclipse Observations

Published online by Cambridge University Press:  25 April 2016

Byron W. Soulsby*
Affiliation:
32 Greenglade Drive, Paradise, South Australia 5075

Abstract

The current ephemerides include an allowance for umbral oblateness based on the flattening of the Earth’s geodetic reference spheroid; there are few published estimates for umbral oblateness derived directly from the geometry of a lunar eclipse. This paper reports umbral oblateness values which have been derived from 7,400 crater contact timing observations of twenty-one lunar eclipses by amateur and professional astronomers since 1972. The observed umbral oblateness was found to be typically three times the geodetic reference spheroid flattening.

Type
Solar and Solar System
Copyright
Copyright © Astronomical Society of Australia 1992

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