| Sutton Bonington weather station | Reino Unido | — | — |
| SVH Observatory | Estados Unidos | Blairstown | — |
 SVOM | Francia | — | — |
| Swan Hill observatory | Australia | Swan Hill | — |
| Swedenborg observatory | Suecia | Langballig | — |
| SWF observatory | Reino Unido | Chelmsford | — |
| SWGO (Observatorio de Rayos Gamma de Campo Amplio del Sur) | — | — | — |
 Swift | Estados Unidos | — | — |
| Swilken Brae observatory | Reino Unido | Saint Andrews | — |
| Szamotuly-Galowo observatory | Polonia | Gałowo | — |
| Szeged Observatory | Hungría | Szeged | — |
| São Paulo Observatory | Brasil | São Paulo | — |
| Sögel observatory | Alemania | Sögel | — |
 Table Mountain Observatory | Estados Unidos | Big Pines | 2.285 m |
| Tacande Observatory | Canarias | El Paso | — |
| Tachibana Observatory | Japón | Miyakonojō | — |
| Taeduk Radio Astronomy Observatory | Corea del Sur | — | 109 m |
| Tajimi observatory | Japón | Tajimi | — |
| Takanezawa observatory | Japón | Takanezawa | — |
 Takapuna observatory | Nueva Zelanda | Auckland Region | — |
 Talcott house | Países Bajos | Leiden | — |
| Talcott Mountain Science Center | Estados Unidos | Connecticut | — |
 Tallinn Observatory | Estonia | Tallinn | 57,8 m |
| Tamanrasset Magnetic Observatory | Argelia | Tamanrasset | — |
| Tamaris Observatory | Francia | La Seyne-sur-Mer | — |
 Tamke-Allan Observatory | Estados Unidos | Tennessee | — |
| Tamworth Observatory | Australia | Tamworth | — |
| Tangra observatory | Australia | St. Clair | — |
| Tara Observatory | Estados Unidos | Pontotoc | — |
| Tarbatness Observatory | Reino Unido | Highland | — |
| Tarleton State University Observatory | Estados Unidos | Stephenville | — |
| Tarzana observatory | Estados Unidos | Los Ángeles | — |
| Tashkent observatory | Uzbekistán | Taskent | — |
| Tataka observatory | República de China | Sinyi Township | — |
| Tatuoca Geomagnetic Observatory | Brasil | Pará | — |
| Taunton observatory | Estados Unidos | Taunton | — |
| Taurus Australis Observatory | Brasil | Taguatinga | — |
 Taurus Hill observatory | Finlandia | Varkaus | — |
 Taurus-1 Observatory | Bielorrusia | Provincia de Vítebsk | — |
 Tavolaia astronomical observatory | Italia | Santa Maria a Monte | — |
| Taylor Range Observatory | Australia | Brisbane | — |
 Tbilisi Observatory | Georgia | Tiflis | — |
| Tebbutt Observatory | Estados Unidos | Edgewood | — |
| TechDome observatory | Estados Unidos | Weed Lookout Tower | — |
| Telescope Live | España | Cortijo de las Minas | — |
| Telescope Live observatory | Chile | Río Hurtado | — |
 Telescopio de modulación de rayos X duros | República Popular China | — | — |
 Telescopio espacial Hubble | — | — | — |