Sierrita Observatory is a private astronomical observatory established by astronomer Dr. Michael Newberry for scientific research and educational purposes. The observatory is located at 975m elevation southwest of Tucson, Arizona, and 15 miles east of Kitt Peak National Observatory. This location is away from cross-continental flight paths and thus free of jet contrails, and it experiences cloud cover and rainfall patterns similar to Kitt Peak. The city of Tucson, Arizona is around 30 miles to the northeast and blocked from line-of-sight by the Tucson Mountains — although the city’s glow, primarily from Sodium Vapor lights, scatters off the atmosphere to brighten the low northeastern sky up to around 30° altitude over azimuths 30° to 70°. The horizon is dark over other azimuths.

The typical zenith brightness is around 21.5 V-mag, with values as low as 21.7 and as bright as 21.3 following a rain or dust storm. At 45° elevation in the direction of Tucson, the sky brightness is typically around 21.3 V-mag. Expressing this in eyeball terms, the Zodiacal Light in the western sky extends to about 80° elevation while, in the eastern sky, the Milky Way in Auriga is readily visible at 30° elevation directly above Tucson.

Thanks to the Pima County lighting ordinance for the protection of observatory skies, the observatory’s dark skies are protected at or near their current state long-term by its location in zone E1-c, a few miles outside the “naturally dark” E1-a zone centered on Kitt Peak. The E1-c zone extends over a 35-mile radius about the summit of Kitt Peak and thus extends 18 miles east, and 23 miles northeast toward Tucson. From Sierrita Observatory, the nearest street light is a sodium vapor lamp with full-cutoff shielding over the horizon, a round 5 miles to the northeast.

Observatory Director: Michael Newberry, Ph.D.

Page header image: Lagoon and Trifid Nebulae in Sagittarius. Nikon D800e, 200mm f/3.2, 60sec @ ISO 1600.