Night Skies Data Report: Photometric Assessment of Night Sky Quality at Point Reyes National Seashore
Meyer EW . 2025. Night Skies Data Report: Photometric Assessment of Night Sky Quality at Point Reyes National Seashore. Science Report. NPS/SR—2025/333. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2314452
This report characterizes night sky conditions in Point Reyes National Seashore (PORE) 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 2 sites. These ground-based observations were collected on 2 nights: May 26, 2008 and September 18, 2009. Satellite data from 2024 was used to create a map of predicted night sky conditions in and around the park. The sky overhead remains in good to moderate condition with the average zenith brightness of 21.62 mag/arcsec2. We estimate more than 79% naked eye stars remained visible under the measured sky brightness, providing a moderate opportunity to view the natural night sky from the park during a cloudless moonless night. The whole sky over PORE is 106%–190% (mean = 148%) brighter than average natural levels, indicating degraded dark sky conditions on average. The main impacts on PORE’s night sky quality were the light domes from Inverness, San Francisco, Point Reyes Station, Petaluma, Novato, Santa Rosa, Oakland, Richmond, San Rafael, and Rohnert Park. The landward light dome observed along the north and eastern horizon exceeds the natural brightness of the Milky Way.
- Type
- Published Report
- Authors
- Meyer, Erik
- Date of Issue
- 2025-07
- Publisher
- National Park Service
- DOI
- 10.36967/2314452
- Units
- NRSS , PORE
- Keywords
- brightness, light pollution, night skies, night sky, photometric assessment, sky quality