#mpc

The IAU Minor Planet Center list of observatory codes as an API — every site the MPC uses to identify a telescope when it publishes astrometric observations of asteroids and comets. For each of 2,700+ codes: the 3-character code, the observatory name, its east longitude and the parallax constants (rho·cos φ', rho·sin φ'). From those constants the API derives each site's geocentric latitude and a -180..180 longitude, so you can find the observatories nearest any point on Earth with a great-circle (haversine) search. Look one up by code, search by name, list them all, or find the closest sites to a latitude/longitude. Distinct from telescope-api (optics maths) — this is the registry of real observing sites and where they are. Served from memory — always fast.

api.oanor.com/observatories-api