| S.O.S. observatory | Estados Unidos | Minneapolis | — |
| Saarbruecken Rastpfuhl observatory | Alemania | Sarrebruck | — |
| Sabah State al-Biruni Observatory | Malasia | Sabah | — |
| Sabino Canyon Observatory | Estados Unidos | Tucson | — |
| Sable Island Magnetic Observatory | Canadá | Nueva Escocia | 5 m |
| SADR observatory | Chile | Río Hurtado | — |
| Saguaro Observatory | Estados Unidos | Tucson | — |
| Saint Barthelemy observatory | Italia | Aosta | — |
| Saint Petersburg Magnetic Observatory | Rusia | — | — |
| Saint-Caprais observatory | Francia | Rabastens-de-Bigorre | — |
| Saint-Felicien observatory | Canadá | Saint-Félicien | — |
 Saint-Malo marigraph | Francia | Saint-Servan | — |
| Saint-Saturnin-les-Avignon Observatory | Francia | Saint-Saturnin-lès-Avignon | — |
| Saint-Sulpice Observatory | Francia | Saint-Sulpice | — |
| Sainte Helene Observatory | Francia | Sainte-Hélène | — |
| Sainte-Clotilde observatory | Francia | Reunión | — |
| Sakai Observatory | Japón | Sakai | — |
| Sakamoto Hachiryu Observatory | Japón | prefectura de Kumamoto | — |
| Sakamoto Observatory | Japón | Ōtsu | — |
| Saku observatory | Japón | Saku | — |
 Sakurajima Volcano Research Center | Japón | Sakurajima Yokoyama-chō | — |
| Salida observatory | Estados Unidos | Salida | — |
 Saltsjöbaden Observatory | Suecia | provincia de Estocolmo | 50 m |
| Salvador astronomical observatory | Argentina | Asociación Atlética Estudiantes | — |
| Salvatore di Giacomo observatory | Italia | Nápoles | — |
| Salvia Observatory | Francia | Saulges | — |
| Samford Valley Observatory | Australia | Samford | — |
| San Benedetto Po observatory | Italia | San Benedetto Po | — |
| San Clemente observatory | Estados Unidos | San Clemente | — |
| San Costantino observatory | Italia | San Costantino | — |
| San Defendente Observatory | Italia | San Defendente | — |
| San Emigdio Peak observatory | Estados Unidos | California | — |
| San Fernando Magnetic Observatory | España | — | — |
| San Gabriel Observatory | España | Alicante | — |
| San Juan Magnetic Observatory | Estados Unidos | — | — |
| San Lazzaro di Savena observatory | Italia | Ponticiella | — |
| San Marco Observatory | Italia | Salerno | — |
| San Pablo-Toledo Magnetic Observatory | España | — | — |
| San Pedro Valley Observatory | Estados Unidos | Benson | — |
| San Pere observatory | España | Mataró | — |
| San Polo A Mosciano observatory | Italia | Scandicci | — |
| Sanderphil Urban Observatory | Italia | Port of Civitavecchia | — |
| Sandia View observatory | Estados Unidos | Río Rancho | — |
| Sandlot observatory | Estados Unidos | Kansas | — |
| Sandvreten Observatory | Suecia | Åloppe | — |
| Sandwich Bay Bird Observatory | Reino Unido | — | — |
| Sanglok Observatory | Tayikistán | Khatlon Province | — |
| Sant Celoni observatory | España | San Celoni | — |
| Sant Gervasi Observatory | España | Vallvidrera, el Tibidabo i les Planes | — |
| Santa Coloma de Gramenet observatory | Italia | Siena | — |
| Santa Mama observatory | Italia | Arezzo | — |
| Santa Maria Magnetic Observatory | Portugal | Azores | 196 m |
| Santa Pola Observatory | España | Santa Pola | — |
| Santana Observatory | Estados Unidos | California | — |
| Santiago-San Bernardo observatory | Chile | Santiago de Chile | — |
| Santorini Volcano Study and Monitoring Institute | Grecia | — | — |
 Sapporo Astronomical Observatory | Japón | Chūō-ku | — |
 Sapporo Science Center | Japón | Sapporo | — |
 SARA-CT | Chile | Región de Coquimbo | 2.123 m |
 SARA-KP | Estados Unidos | Arizona | 2.133 m |
| Sassoeiros observatory | Portugal | Freguesia de Carcavelos | — |
| SATech-01 | — | — | — |
 Satellite Communications Center, Medvezh'i Ozyora | Rusia | Dolgoye Lyodovo village | 200 m |
| SATINO Remote observatory | Francia | Saint-Michel-l'Observatoire | — |
 Satélite de Sondeo de Exoplanetas en Tránsito | Estados Unidos | — | — |
| Sauro Donati Astronomical Observatory | Italia | Lucca | — |
| Savelli Observatory | Italia | Savelli | — |
| Savigny-le-Temple observatory | Francia | Savigny-le-Temple | — |
 Sayan Solar Observatory | Rusia | Mondy | — |
| Sayre Observatory | Estados Unidos | South Bethlehem | — |
| Schaerding observatory | Austria | 178243 Schaerding | — |
| Schafmatt Observatory | Suiza | Oltingen | 819 m |
| Schela Observatory | Rumania | — | — |
| Scheuren Observatory | Alemania | Alemania | 200 m |
| Schmelz Observatory | Francia | Schmelz | — |
| Schmidt Observatory System | — | — | — |
| Schonfeld observatory | Alemania | Schönfeld-Weißig | — |
| School for Inclement Weather | — | — | — |
| Schothorst Public Observatory | Países Bajos | Amersfoort | — |
| Schuelerlabor Astronomie St. 7 observatory | Alemania | Wuppertal | — |
| Schwerin observatory | Alemania | Schwerin | — |
| Scott Base Magnetic Observatory | — | — | — |
| Scott Observatory | Estados Unidos | Fitchburg | — |
 Scottish Dark Sky Observatory | Reino Unido | East Ayrshire | — |
| Seagrave Memorial Observatory | Estados Unidos | — | — |
 Sears Tower – Harvard Observatory | Estados Unidos | Cambridge | — |
| Sedgefield observatory | Sudáfrica | Sedgefield | — |
| Segorbe observatory | España | Segorbe | — |
| Seismic Research Centre | Dominica | — | — |
| Seismic Station in Serra do Pilar | Portugal | Santa Marinha e São Pedro da Afurada | — |
| Seismic station Kašperské Hory | República Checa | Kašperské Hory | — |
| Seismological Observatory Gräfenberg | — | — | — |
| Seiwa Kogen Observatory | Japón | — | — |
| Selangor Observatory | Malasia | Sabak Bernam | — |
| Sencelles observatory | España | Sencelles | — |
 Sendai Astronomical Observatory | Japón | Nishikigaoka | 163 m |
| Sendai Astronomical Observatory Ayashi Station | Japón | Shimoayashi | — |
| Sendai Municipal Observatory | Japón | Sendai | — |
 Sendai Space Museum | Japón | Nagatoshi-chō | — |
| Sendling Observatory | Alemania | Sendling | 583 m |
| Senftenberger observatory | República Checa | Řeřichy | — |
| Sengamine Observatory | Japón | Kami | — |
| Serra La Nave observatory | Italia | Ragalna | 1.735 m |
| Serra Observatory | Italia | Prelo | — |
 Servicio Geológico de Canadá | Canadá | Ottawa | — |
 Servicio internacional de latitud | Estados Unidos | — | — |
| Seveso observatory | Italia | provincia de Monza y Brianza | — |
| SGT Observatory | Austria | Gaflenz | — |
| Shahe Station (Beijing Observatory) | República Popular China | Pekín | — |
| Shandong University observatory | República Popular China | Weihai | — |
| Sharjah Observatory | Emiratos Árabes Unidos | Sarja | — |
| Shasta Valley Observatory | Estados Unidos | Gazelle | — |
 Shattuck Observatory | Estados Unidos | Nuevo Hampshire | — |
| Shed of Science South observatory | Estados Unidos | Pontotoc | — |
| Sheep Hill Observatory | Estados Unidos | Boonton | — |
| Sheikh Tahir Astronomical Center | Malasia | Penang | — |
| Sheltozero Station Observatory | Rusia | Shyoltozero | 42 m |
| Shenton Park observatory | Australia | Shenton Park | — |
| Sherbrooke observatory | Canadá | Sherbrooke | — |
 Sherwood Observatory | Reino Unido | Distrito de Ashfield | — |
| Sherzer Observatory | Estados Unidos | Míchigan | — |
 Sheshan Observatory | República Popular China | Sheshan | — |
| Shimada observatory | Japón | Shimada | — |
| Shimotsuma observatory | Japón | Shimotsuma | — |
| Shinshiro observatory | Japón | Aichi Prefectural Xincheng East High School | — |
| Shishikui observatory | Japón | Shishikui | — |
| Shizuoka observatory | Japón | Shizuoka | — |
 Shosanbetsu observatory | Japón | Prefectura de Hokkaido | — |
| Shumagin Magnetic Observatory | Estados Unidos | — | — |
| Siberian State Aerospace University Observatory | Rusia | Krasnoyarsk | 160 m |
| Siding Spring Observatory: iTelescope Observatory | Australia | Siding Spring | — |
| Siding Spring-Janess-G, JAXA | Australia | Siding Spring | — |
| Siding Spring-LCO A | Australia | Coonabarabran | — |
| Siding Spring-LCO B | Australia | Coonabarabran | — |
| Siding Spring-LCO Clamshell #1 | Australia | Coonabarabran | — |
| Siding Spring-LCO Clamshell #2 | Australia | Coonabarabran | — |
| Sidoli observatory | Argentina | Luis Guillón | — |
| Siegen observatory | Alemania | Siegen | — |
| Siena observatory | España | Ager | — |
| Sierra Contraviesa observatory | España | Los Vargas | — |
| Sierra Remote observatory | Estados Unidos | Auberry | — |
| Sierra Sinagua Observatory | Estados Unidos | Flagstaff | — |
| Sierra Stars observatory | Estados Unidos | Mesa Vista | — |
| Signilskär Bird Observatory | Finlandia | Hammarland | — |
 Silesian Planetarium | Polonia | Chorzów | 316 m |
 Siligo astronomical observatory | Italia | Siligo | — |
| Silver Spring observatory | Estados Unidos | White Oak | — |
 SIM Lite Astrometric Observatory | — | — | — |
 Simplesat | — | — | — |
 Sinnott Memorial Observation Station | Estados Unidos | Klamath County | 2.027 m |
| Sinsen observatory | Alemania | Sinsen-Lenkerbeck | — |
| Sintini observatory | Italia | Alfonsine | — |
| Sirius observatory | España | Las Lomas | — |
 Sistema estereoscópico de alta energía | Namibia | Khomas Region | 1.800 m |
| Sitka Magnetic Observatory | Estados Unidos | — | — |
| SKA Telescope, Australia | Australia | Western Australia | — |
| Skibotn Astrophysical Observatory | Noruega | Skibotn | — |
 Skinakas Observatory | Grecia | — | 1.750 m |
| Skokholm Bird Observatory | Reino Unido | — | — |
| Sky Vistas observatory | Austria | Eichgraben | — |
 Sky's the Limit Observatory and Nature Center | Estados Unidos | Twentynine Palms | — |
| Skybor Observatory | España | Borja | — |
| Skygems Namibia Remote Observatory | Namibia | 82346 Hakos | — |
| Skyledge Observatory | Estados Unidos | Killingworth | — |
| Skylive observatory | Italia | Catania | — |
 SkyMapper | Australia | New South Wales | 1.163 m |
| Sliven Observatory | Bulgaria | Sliven | — |
| Slooh.com Canary Islands observatory | España | Parque Nacional del Teide | — |
| Slooh.com Chile Observatory | Chile | Lo Barnechea | — |
| Slope Rock observatory | Finlandia | Hyvinkää | — |
 Slottsskogsobservatoriet | Suecia | Municipalidad de Gothenburg | — |
 Slovak Central Observatory Hurbanovo | Eslovaquia | Hurbanovo | 115 m |
 Small Astronomy Satellite 2 | Estados Unidos | — | — |
 Small Astronomy Satellite 3 | Estados Unidos | — | — |
 Smeetoren | Países Bajos | Utrecht | — |
| Smith College Observatory | Estados Unidos | Northampton | — |
| Smith Observatory and Dr. William R. Brooks House | Estados Unidos | Nueva York | — |
| Smith River Observatory | Estados Unidos | Danbury | — |
| Smolecin observatory | Polonia | Smolęcin | — |
| Smolyan Planetarium | Bulgaria | Smolyan | — |
| Snohomish Hilltop Observatory | Estados Unidos | Snohomish | — |
| Snow King Observatory and Planetarium | Estados Unidos | — | — |
| Sobaeksan Optical Astronomy Observatory | Corea del Sur | Danyang | 1.378 m |
| Sobradillo observatory | España | Sobradillo de Palomares | — |
| Sodankyla Magnetic Observatory | Finlandia | Sodankylä | — |
| Soerth observatory | Alemania | Sörth | — |
 SOFIA | — | — | — |
 Sofia University Astronomical Observatory | Bulgaria | Sredets | — |
 Sohland/Spree observatory | Alemania | Sohland an der Spree | 335 m |
 SOHO | — | — | — |
| Soisy-sur-Seine observatory | Francia | Soisy-sur-Seine | — |
| Sola Fide Observatory | Estados Unidos | Condado de Mower | — |
 Solar Anomalous and Magnetospheric Particle Explorer | — | — | — |
 Solar Monitoring Observatory | — | — | — |
 Solar Observatory - Tower 2 and Tower 3 - external appearance | Austria | Treffen am Ossiacher See | — |
 Solar Observatory - Tower 4 - Appearance | Austria | Arriach | — |
 Solar Observatory Tower Meudon | Francia | Meudon | — |
| Solar Polar Orbit Observatory | República Popular China | — | — |
 Solar Probe Plus | Estados Unidos | — | — |
 Solar Radiation and Climate Experiment | Estados Unidos | — | — |
| Solar Ultraviolet Imaging Telescope | — | — | — |
| Solar-C | — | — | — |
| Solaris observatory | Polonia | — | — |
| Sollies-Pont observatory | Francia | Solliès-Pont | — |
 Sommers–Bausch Observatory | Estados Unidos | Colorado | — |
| SON Station | Chile | San Pedro de Atacama | — |
 Sonda Einstein | República Popular China | — | — |
| SONEAR Observatory | Brasil | Minas Gerais | — |
| SONEAR Observatory | Brasil | — | — |
| Sonmiani Magnetic Observatory | Pakistán | — | — |
| Sonoita Research observatory | Estados Unidos | Sonoita | — |
 Sonoma State Observatory | Estados Unidos | California | — |
| Sonoran Skies observatory | Estados Unidos | St. David | — |
| Sooke observatory | Canadá | Sooke | — |
| Sopot Astronomical Observatory | Serbia | Sopot | — |
| Sormano 2 Observatory | Italia | Villa Melzi de Eril | — |
| South African Radio Astronomy Observatory | Sudáfrica | — | — |
 South cupola of Brno Observatory and Planetarium | República Checa | Veveří | — |
| South Meridian Marker | Reino Unido | Ballyheridan | — |
| South Observatory | Reino Unido | Waterlooville | — |
 South Pole Atmospheric Research Observatory | — | — | — |
| South Wonston observatory | Reino Unido | South Wonston | — |
| Southeastern Arizona Bird Observatory | Estados Unidos | — | — |
| Southend Bradfield observatory | Reino Unido | Bradfield | — |
| Southern Photometric Local Universe Survey Telescope | Chile | — | — |
| Southern Stars Observatory | Francia | Faaa | — |
| Southern Utsunomiya observatory | Japón | Utsunomiya | — |
| Southland Astronomical Society Observatory | Nueva Zelanda | — | — |
| Southwater observatory | Reino Unido | Southwater | — |
| Southwest Institute for Space Research | Estados Unidos | New Mexico | — |
| Sozzago astronomical Station | Italia | Sozzago | — |
 Space Research Centre, Polish Academy of Sciences | Polonia | Breslavia | — |
| Space Tracking and Communications Center, JAXA | Japón | Ibara | — |
| Spaceguard Centre | Reino Unido | Powys | — |
| Spacelab Solar | — | — | — |
| SPAG Monfrague observatory | España | Palazuelo-Empalme | — |
| SPARCS | Estados Unidos | — | — |
| SPARTAN 201-05 | — | — | — |
| Specola Solare Ticinese | Suiza | Locarno | — |
| Specula | Hungría | Eger | — |
 SPECULOOS-South Observatory | Chile | Provincia de Antofagasta | — |
 Spektr-RG | — | — | — |
 SPHEREx | Estados Unidos | — | — |
 Sphinx | Suiza | distrito de Goms | 3.571 m |
| Spica observatory | Italia | Carmignano | — |
| Spider | — | — | 36.000 m |
| Spirit Marsh Observatory | Estados Unidos | Meire Grove | — |
| SpringBok Observatory | Namibia | Khomas Region | — |
| Springe observatory | Alemania | Springe | — |
| Spurn Bird Observatory | Reino Unido | — | — |
| Squirrel Valley Observatory | Estados Unidos | Columbus | — |
| St John's Magnetic Observatory | Canadá | — | — |
| St Paul Observatory | Francia | Reunión | — |
| St-Martin Observatory | Francia | Amathay-Vésigneux | — |
 St. Andrews observatory | Reino Unido | Fife | — |
| St. George Observatory | Rumania | Cocoșești | — |
| St. Helena Magnetic Observatory | — | — | 586 m |
 St. Margarethen observatory | Suiza | Binningen | — |
| St. Mellons observatory | Gales | Cardiff | — |
| St. Michel sur Meurthe observatory | Francia | Saint-Michel-sur-Meurthe | — |
| St. Thomas Observatory | Estados Unidos | — | — |
| Staatliche Vogelschutzwarte Garmisch-Partenkirchen | Alemania | Garmisch-Partenkirchen | — |
| Stakenbridge observatory | Reino Unido | Kidderminster | — |
| Stamford observatory | Estados Unidos | Stamford | — |
| Stammersdorf observatory | Austria | Stammersdorf | — |
| Stanley Laver Observatory | Reino Unido | Pontesbury | — |
| Stansbury Park Observatory Complex | Estados Unidos | Tooele | — |
| Star Cruiser Observatory | Estados Unidos | Anza | — |
| Star Ridge observatory | Estados Unidos | Weimar | — |
 Star Square Astronomical Observatory | Japón | Shimizu-ku | — |
 Stara Lesna observatory | Eslovaquia | Stará Lesná | 785 m |
 Stardome Observatory | Nueva Zelanda | Auckland Region | — |
| Stardreams Observatory | Rumania | Vălenii de Munte | — |
| Stardust Observatory | Rumania | Brașov | — |
| Starhoo Observatory | Estados Unidos | Lakeville | — |
 Starkenburg Observatory | Alemania | Heppenheim | 256 m |
| Starkenburg Observatory Heppenheim Asteroid Survey (SOHAS) | Alemania | Heppenheim | — |
| Starlab Observatory | Rusia | Nizhny Arkhyz | — |
| Starlight Observatory | República Popular China | Condado de Anji | — |
| Starry Knight observatory | Estados Unidos | California | — |
| Starry Night Observatory | Estados Unidos | Glidden | — |
| Starry Wanderer observatory | Bielorrusia | Baran | — |
| STARS-AO | Japón | — | — |
 Stará hvězdárna | República Checa | Valašské Meziříčí | — |
| Stazione Astronomica Betelgeuse observatory | Italia | Magnago | — |
| Stazione Astronomica Le Pleiadi | Italia | Taverna | — |
 Stellafane | Estados Unidos | Springfield | — |
| Stellarium Gornergrat | Suiza | Zermatt | — |
| Stennis Space Center Magnetic Observatory | Estados Unidos | — | — |
| Stephanion Observatory | Grecia | — | — |
| Stephens Observatory | Estados Unidos | Maine | — |
 STEREO-A | — | — | — |
| STEREO-B | — | — | — |
 Sterngarten | Austria | Mauer | 329 m |
| Sterni Observatory | Alemania | Kempten | — |
 Sternwarte Aachen | Alemania | Aachen-Mitte | 204 m |
 Sternwarte Bülach | Suiza | Bülach | — |
| Sternwarte Calden | Alemania | Calden | — |
 Sternwarte Davidschlag | Austria | Kirchschlag bei Linz | 815 m |
| Sternwarte Feuerstein | Alemania | Ebermannstadt | 500 m |
| Sternwarte Greifswald | Alemania | Greifswald | 9 m |
 Sternwarte Herne | Alemania | Herne | 52 m |
 Sternwarte Hof | Alemania | Hof | — |
| Sternwarte Kassel | Alemania | Kassel | — |
 Sternwarte Kirchheim | Alemania | Amt Wachsenburg | 267 m |
| Sternwarte Limburg | Alemania | Limburgo del Lahn | — |
| Sternwarte Metzerlen | Suiza | Soleura | — |
 Sternwarte Mirasteilas | Suiza | Falera | — |
 Sternwarte Neanderhöhe Hochdahl | Alemania | Erkrath | 137 m |
| Sternwarte Neuenhaus | Alemania | Neuenhaus | 18 m |
 Sternwarte Rümlang | Suiza | Rümlang | — |
 Sternwarte Simplon-Adler | Suiza | Simplon | — |
| Sternwarte Sirius | Suiza | Sigriswil | — |
| Sternwarte Tentlingen | Suiza | Tentlingen | — |
 Sternwarte Tübingen | Alemania | Tubinga | 470 m |
 Sternwarte und Planetarium „Sigmund Jähn“ Rodewisch | Alemania | Rodewisch | — |
 Sternwarte Weikersheim | Alemania | Weikersheim | 332 m |
 Sternwarte Welzheim | Alemania | Welzheim | 547 m |
| Sternwarte Wetzikon | Suiza | Wetzikon | — |
 Sternwarten des ehemaligen Forschungsinstituts Manfred von Ardenne | Alemania | Dresde | — |
| Sterrenwacht Andromeda observatory | Países Bajos | Ellecom | — |
| Sterrenwacht Gooi en Vechtstreek | Países Bajos | — | — |
 Sterrenwacht Limburg | Países Bajos | Heerlen | — |
| Sterrenwacht Rijswijk | Países Bajos | Rijswijk | — |
| Stia observatory | Italia | Stia | — |
| Stixendorf observatory | Austria | Stixendorf | — |
 Stjerneborg | Suecia | Municipio de Landskrona | — |
| Stockholm Observatory | Suecia | provincia de Estocolmo | — |
| Stockport observatory | Australia | Stockport County Football Club | — |
| Stokesville Observatory | Estados Unidos | Virginia | — |
| Stone Edge observatory | Estados Unidos | El Verano | — |
| Stone Finder Observatory | Canadá | Calgary | — |
| Stonegate Observatory | Estados Unidos | Ann Arbor | — |
 Stonehenge Aotearoa | Nueva Zelanda | Carterton District | — |
 Stony Ridge Observatory | Estados Unidos | California | 1.730 m |
 Stonyhurst Observatory | Reino Unido | — | — |
| Stowupland observatory | Reino Unido | Stowmarket | — |
 Stratoscope | — | — | — |
| Strawberry Field observatory | Reino Unido | City of Southampton | — |
| Student Astronomical Observatory, Department of Astronomy - Plana | Bulgaria | Stolichna obshtina | — |
| Stull Observatory | Estados Unidos | Nueva York | — |
| Stuttgart-Hoffeld observatory | Alemania | Stuttgart | — |
| Submillimeter Array, Mauna Kea (SMA) | Estados Unidos | Hilo | — |
 Submillimeter Wave Astronomy Satellite | Estados Unidos | — | — |
| Sudair Observatory | Arabia Saudí | Provincia de Riad | 915 m |
 Sudbury Neutrino Observatory | Canadá | Ontario | — |
| Sukagawa observatory | Japón | Sukagawa | — |
| Sulphur Flats observatory | Estados Unidos | Jémez Springs | — |
 Sulphur Mountain Cosmic Ray Station | Canadá | Improvement District No. 09 (Banff National Park) | — |
 Sultan Ismail Building | Malasia | Kota Iskandar | — |
| Sumoto observatory | Japón | Sumoto | — |
 Sun Dagger site | Estados Unidos | condado de San Juan | — |
| Sun Watcher using Active Pixel System Detector and Image Processing | — | — | — |
| Sundre bird observatory | Suecia | — | — |
| Sunflower Observatory | Estados Unidos | Olathe | — |
| Sunflower Observatory | Estados Unidos | Regal Santa Fe | — |
| Sunhill Observatory | Estados Unidos | Newton | — |
| Sunrise | — | — | — |
| Sunriver Nature Center observatory | Estados Unidos | Sunriver | — |
 Sunriver Observatory | Estados Unidos | Oregón | — |
| Sunspot Solar Observatory | Estados Unidos | condado de Otero | — |
| Suntopia Marina observatory | Japón | Sumoto | — |
| SUNY Oneonta College Observatory | Estados Unidos | Nueva York | — |
 Super-Kamiokande | Japón | Hida | — |
| Supernova/Acceleration Probe | — | — | — |
| Sura Gardens | Ucrania | Kam'yanka | — |
| Surlari Magnetic Observatory | Rumania | Ilfov | 84 m |
| Surlari National Geomagnetic Observatory | Rumania | — | — |
| Sutherland Observatory | Sudáfrica | Karoo Hoogland | — |
| Sutherland-LCO A | Sudáfrica | Karoo Hoogland | — |
| Sutherland-LCO Aqawan A #1 observatory | Sudáfrica | Sutherland | — |
| Sutherland-LCO B | Sudáfrica | Karoo Hoogland | — |
| Sutherland-LCO C | Sudáfrica | Karoo Hoogland | — |
| 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 | — |