A Gallery of Sky Brightness Curves from the January 2019 Total Lunar Eclipse

Volume 48 number 1 (2020)

Jennifer J. Birriel: Department of Physics, Earth Science, and Space Systems Engineering, Morehead State University, 150 University Boulevard, Morehead, KY 40351; j.birriel@moreheadstate.edu, jkadkins@moreheadstate.edu
J. Kevin Adkins: Department of Physics, Earth Science, and Space Systems Engineering, Morehead State University, 150 University Boulevard, Morehead, KY 40351; j.birriel@moreheadstate.edu, jkadkins@moreheadstate.edu
Andrea Bertolo: Regional Environmental Prevention and Protection Agency of Veneto, Via Ospedale Civile 24, Padova, Italy; andrea.bertolo@arpa.veneto.it
Rainer Ehlert: Citizen Scientist, Observatorio Real de 14, Cto. Real de Catorce #145, 78216 San Luis Potosí, San Luis Potosí, Mexico; rsfoto@rsfotografia.com
Michael McKeag: IDA Delegate, IDA Oregon Director, P. O. Box 130, Mosier, OR 97040; michael.mckeag@darksky.org
Salvador J. Ribas: Parc Astronomic Montsec - Ferrocarrils de la Generalitat de Catalunya, Cami del coll d'Ares s/n, E25691 Ager, Lleida, Spain; sjribas@parcastronomic.cat
Anthony Tekaatch: Unihedron, 4 Lawrence Avenue, Grimsby, Ontario L3M 2L9, Canada; anthony@unihedron.com

Abstract

On the night of 20–21 January 2019, a total lunar eclipse occurred for all of the Americas and most of Africa and Western Europe. We present a gallery of night sky brightness curves taken during the eclipse from eleven locations distributed through the Americas and Western Europe. Each data set was acquired using Unihedron Sky Quality Meter (SQM) pointed at zenith. In most cases, it is easy to identify the eclipse signature for the partial and total eclipse phase. The penumbral phase is undetectable due to the increasing brightness at zenith as the lunar altitude increases. A site located near the Tropic of Cancer in Mexico displays the most unusual curve: as the moon emerges from totality, the lunar altitude is very near zenith resulting in a rapid increase in brightness. These results can serve as a reference for future lunar eclipse observations using an SQM device pointed at zenith. We use the data to determine the length of the totality phase, to compare totality brightness to each site’s brightness on a clear, new moon night, and finally to estimate the size of Earth’s umbral shadow. Ideal observation sites would be located in the mid-latitudes of either hemisphere. We suggest future eclipse observations with SQMs be accompanied by contemporaneous all-sky imaging and data from a cloud sensor and weather station at each site to better understand the effects of lunar altitude and clouds in the field of view of each individual SQM.