| Sunflower Observatory | Olathe | — |
| Sunflower Observatory | Regal Santa Fe | — |
| Sunhill Observatory | Newton | — |
| Sunriver Nature Center observatory | Sunriver | — |
 Sunriver Observatory | Oregón | — |
| Sunspot Solar Observatory | condado de Otero | — |
| SUNY Oneonta College Observatory | Nueva York | — |
| SVH Observatory | Blairstown | — |
 Swift | — | — |
 Table Mountain Observatory | Big Pines | 2.285 m |
| Talcott Mountain Science Center | Connecticut | — |
 Tamke-Allan Observatory | Tennessee | — |
| Tara Observatory | Pontotoc | — |
| Tarleton State University Observatory | Stephenville | — |
| Tarzana observatory | Los Ángeles | — |
| Taunton observatory | Taunton | — |
| Tebbutt Observatory | Edgewood | — |
| TechDome observatory | Weed Lookout Tower | — |
 Telescopio espacial Nancy Grace Roman | — | — |
| Telescopio extremadamente pequeño de kilogrado | — | — |
 Telescopio Gemini Frederic C. Gillet | Hawaii County | 4.213 m |
 Telescopio Hooker | — | — |
 Telescopio infrarrojo de NASA | Hawaii County | — |
 Telescopio Subaru | Hawái | 4.139 m |
| Telescopio XO | Hawái | — |
 Telescopio óptico infrarrojo | condado de Santa Cruz | — |
| Temecula observatory | Temecula | — |
| Ten Acre Observatory | Oklahoma | — |
| Tenagra II Observatory | Arizona | 1.312 m |
| Terre Haute observatory | Terre Haute | — |
| Texas A&M Astronomical Observatory | Texas | — |
| Texas A&M Physics observatory | College Station | — |
| Texas Star Party, Inc. | — | — |
| The Cottage Observatory | Altoona | — |
 The Octagon at Amherst College | Massachusetts | — |
| The Ranch Observatory | New Mexico | — |
 Theodor Jacobsen Observatory | Seattle | — |
| Thomas G. Cupillari Observatory | Fleetville | — |
| Thomas More College Observatory | Kentucky | — |
| Thompson Observatory | Wisconsin | — |
| Thompsonville Observatory | Thompsonville | — |
| Thornton observatory | Thornton | — |
| Three Buttes observatory | Saddlebrooke | — |
| Three College Observatory | Carolina del Norte | — |
| Tigh Speuran Observatory | Framingham | — |
| Timberlake Observatory | Reston | — |
| Timberland Observatory | Alabama | — |
| Timberline observatory | Winterset | — |