Zenith Sky Brightness and Color during the March 14, 2025 Total Lunar Eclipse

Volume 54 number 2 (2026)

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Jennifer Jean Birriel

Department of Engineering Sciences, Morehead State University, 150 University Boulevard, Morehead, KY 40351; j.birriel@ moreheadstate.edu

Brayden Schwegman

Department of Engineering Sciences, Morehead State University, 150 University Boulevard, Morehead, KY 40351; bjschwegman@moreheadstate.edu

Abstract

During a lunar eclipse, the night sky darkens as the moon enters the umbral region of the Earth’s shadow. Due to the refraction of solar rays by Earth’s atmosphere, the lunar surface is illuminated by red light even during totality. We suggest that sky brightness studies using filtered Sky Quality Meters (SQMs) might help inform atmospheric scattering models. We present observations of zenith sky brightness during the March 14, 2025, total lunar eclipse from Morehead, Kentucky. Data were collected using a set of SQMs fitted with red (R), green(G), blue (B), and clear or luminous (L) filters. During totality, zenith sky brightness viewed through the L band was 19.0 ± 0.1 mag / arcsec^2 (in SQM magnitudes), in agreement with previous measurements made at this site during the January 19, 2019, lunar eclipse. The B–G color index shows little observable difference between B and G bandpasses. The B–R color index increases by 0.30 ± 0.14 mag / arcsec^2 during totality vs post totality, indicating a “reddening” of zenith sky color during totality. This is consistent with the red appearance of the Moon during totality.