San Juan Magnetic Observatory

San Juan Magnetic Observatory is a geomagnetic observatory run under the USGS Geomagnetism Program, sited on a 36-acre facility in the mountains near Cayey, Puerto Rico, in the United States.

About San Juan Magnetic Observatory

The observatory measures vector and scalar magnetometer data, contributing to Earth main-field modelling, geophysics research, space physics research, and space weather assessment — work that depends on stable, continuous long-term monitoring rather than public telescope viewing.

History

Operations began in 1903 as part of the USGS Geomagnetism Program. The observatory moved to its current mountain site near Cayey in 1965, where it has operated since. Its data recording has also advanced over time: measurements were archived with INTERMAGNET at 1-minute resolution until mid-2011, and at 1-second resolution from June 13, 2011 onward.

Location & getting there

The site sits in the mountains near Cayey, Puerto Rico, part of our North America region listing — a location chosen for its distance from the electrical and magnetic interference of denser urban development.

Visiting San Juan Magnetic Observatory

As a working scientific monitoring station rather than a public astronomy venue, we have not confirmed general visiting hours or tours. Check with the USGS Geomagnetism Program directly for any access arrangements.

See your named star from here

Though its own instruments watch the Earth rather than the sky, the mountains around Cayey share the dark, remote qualities that suit stargazing — and a named star's coordinates work the same way anywhere on the island. Browse our catalogue or name a star to get your own.