Night skies data report: Photometric assessment of night sky quality at Haleakalā National Park

Meyer, Erik

doi:10.36967/2305714

This report characterizes night sky conditions in Haleakalā National Park (HALE) 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 3 nights from 2012-06-12 to 2012-06-14. 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 the average zenith brightness of 21.78 mag/arcsec2. We estimate more than 98% of stars were still visible for most of the time, providing an outstanding opportunity to observe the natural night sky from the park. The whole sky over HALE is 11%-18% (mean=14%) brighter than average natural levels, indicating excellent dark sky conditions on average. In HALE, we classified the sky as Bortle Class 3: rural sky, based on the visibility of astronomical objects. The average naked eye limiting magnitude (NELM) is 6.7, which is approaching near pristine under average conditions. Our Sky Quality Meter (SQM) measurements average to 21.74 mag/arcsec2, indicating the zenith is darker than what we can accurately measure with a SQM. Some indication of light pollution is evident along the horizon. Clouds may appear faintly illuminated in the brightest parts of the sky near the horizon but are dark overhead. The Milky Way still appears complex. The main impacts to HALE’s night sky quality were the light domes from Kula, Kihei, Pukalani, Wailea and Kahului. Light domes from these communities were observed along the horizon, although none exceeded the natural brightness of the Milky Way at the time of the study.

Night skies data report: Photometric assessment of night sky quality at Haleakalā National Park

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