Night skies data report: Photometric assessment of night sky quality at Sequoia and Kings Canyon National Parks
Meyer EW . 2025. Night skies data report: Photometric assessment of night sky quality at Sequoia and Kings Canyon National Parks. Science Report. NPS/SR—2025/249. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2308859
This report characterizes night sky conditions in Sequoia and Kings Canyon National Parks (SEKI) using measurements made in the park unit and models of regional conditions based on satellite data. Calibrated night sky imagery was obtained to characterize the night sky at 5 sites. These ground-based observations were collected on 8 nights from 2004-06-12 to 2009-07-21. Satellite data from 2022 was used to create a map of predicted night sky conditions in and around the park. The sky overhead remains pristine with an average zenith brightness of 21.63 mag/arcsec2. We estimate more than 91% of stars were visible throughout the data collection period, providing an excellent opportunity to observe the natural night sky from the park during cloudless, new moon conditions. The whole sky over SEKI is 18%–74% (mean=53%) brighter than average natural levels, indicating impaired dark sky conditions on average. In SEKI, we classified the sky as Bortle Class 4: rural/suburban transition, based on the visibility of astronomical objects. The average naked eye limiting magnitude (NELM) is 6.75, which is approaching near pristine under average conditions. Our Sky Quality Meter (SQM) measurements average 21.74 mag/arcsec2, indicating the zenith is darker than what we can accurately measure with an SQM. Fairly obvious light-pollution domes are apparent over population centers in several directions. The zodiacal light is clearly evident but doesn’t even extend halfway to the zenith at the beginning or end of twilight. The Milky Way well above the horizon is still impressive but lacks all but the most obvious structure. The main impacts on SEKI’s night sky quality were the light domes from Los Angeles, Fresno, Visalia, Bakersfield, Porterville, Clovis, Tulare, Las Vegas, and Hanford. These light domes were observed along the horizon, with a few nearing the natural brightness of the Milky Way.
- Type
- Published Report
- Authors
- Meyer, Erik
- Date of Issue
- 2025-03
- Publisher
- National Park Service
- DOI
- 10.36967/2308859
- Units
- NRSS , NSNSD , SEKI
- Keywords
- brightness, light pollution, night skies, night sky, photometric assessment, sky quality