Measuring Zenith Sky Brightness and Color Changes during the April 8, 2024 Total Solar Eclipse Using Filtered Sky Quality Meters
Volume 54 number 1 (2026)
- Jennifer 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
- Ivan Hargesheimer
- Department of Engineering Sciences, Morehead State University, 150 University Boulevard, Morehead, KY 40351
Abstract
Zenith sky brightness measurements were obtained on the line of totality during the April 8, 2024, total solar eclipse. Observations were made at two sites: Wickliffe, Kentucky, and Oxford, Ohio. A set of four Sky Quality Meters (SQMs) fitted with clear (L), red (R), green (G), and blue (B) filters collected data at each site. During totality, sky brightness dropped to 13.27 ± 0.1 mag / arcsec^2 at Wickliffe, Kentucky, and 12.99 ± 0.1 mag / arsec^2 at Oxford, Ohio. These values are consistent with past eclipse observations and are brighter than nautical twilight. Over the course of the partial eclipse the spectral content prior to totality, as measured by the R–B and G–B indices, remained constant. During totality, the spectral content shifted towards B, consistent with the light arriving at zenith from outside the umbra after multiple scattering events. The spectral content of zenith sky brightness post-totality decreased at a constant rate due to changes in solar altitude. The use of color-filtered SQMs greatly simplifies the data collection process with regards to both photometric and spectrophotometric measurements.