Observatory

Historically, ground-based observatories were as simple as containing a mural instrument (for measuring the angle between stars) or Stonehenge (which has some alignments on astronomical phenomena).

Ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum.

In most cases, the entire upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky.

[citation needed] For optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution.

The ideal locations for modern observatories are sites that have dark skies, a large percentage of clear nights per year, dry air, and are at high elevations.

[3] Sites that meet the above criteria for modern observatories include the southwestern United States, Hawaii, Canary Islands, the Andes, and high mountains in Mexico such as Sierra Negra.

[5][6] Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the central part of Eastern Antarctica.

Some of the world's major radio observatories include the Very Large Array in New Mexico, United States, Jodrell Bank in the UK, Arecibo in Puerto Rico, Parkes in New South Wales, Australia, and Chajnantor in Chile.

Magnetic observations are aggregated, processed, quality checked and made public through data centers such as INTERMAGNET.

[31][32] The types of measuring equipment at an observatory may include magnetometers (torsion, declination-inclination fluxgate, proton precession, Overhauser-effect), variometer (3-component vector, total-field scalar), dip circle, inclinometer, earth inductor, theodolite, self-recording magnetograph, magnetic declinometer, azimuth compass.