| Al Sadeem Observatory | Emiratos Árabes Unidos | Abu Dhabi | — |
| Al-Fulaij observatory | Omán | Al Batinah Sur gobernación | — |
| Al-Khatim Observatory | Emiratos Árabes Unidos | Abu Dhabi | — |
 Al-Khawarizmi Astronomy Complex | Malasia | — | — |
| Al-Ujairi Observatory | — | — | — |
| Alasht Amateur Observatory | — | — | — |
| Albanyà Observatory | España | Albañá | — |
 Alberto do Mónaco observatory | Portugal | — | — |
| Albigneux observatory | Francia | Saint-Héand | — |
| Albireo Observatory | España | Inca | — |
| Albox observatory | España | San Roque | — |
| Alder Springs observatory | Estados Unidos | Alder Springs | — |
| Alderney Bird Observatory | Guernsey | Alderney | — |
 Aldershot Observatory | Reino Unido | Rushmoor | — |
| Alert Magnetic Observatory | Canadá | Nunavut | 60 m |
 Alexander-Frantz-Sternwarte | Alemania | Dresde | — |
| Algarve Observatory | Portugal | Portimão | — |
| Alginet Observatory | España | Alginet | — |
| Ali Observatory | República Popular China | Ngari | 5.047 m |
| Alianza S4 observatory | Argentina | Departamento Calingasta | — |
| Alibag Magnetic Observatory | India | Maharashtra | 0 m |
| Alicante observatory | España | El Campello | — |
| Alice Springs Magnetic Observatory | Australia | Northern Territory | 557 m |
| Aljaraque Observatory | España | Aljaraque | — |
| Allahabad Observatory | — | — | — |
| Allen observatory | Estados Unidos | Bob Dylan | — |
| Allgäuer Volkssternwarte Ottobeuren | Alemania | Ottobeuren | 696 m |
| Alma Ata Magnetic Observatory | Kazajistán | — | 1.300 m |
| Almalex Observatory | Reino Unido | Ciudad de Leeds | — |
| ALMO observatory | Italia | Padulle | — |
| Alnitak observatory | España | El Puerto de Santa María | — |
| ALOMAR | Noruega | Andøy | — |
 Alor Setar Tower | Malasia | Alor Setar | — |
| Alphard Observatory | Italia | Satia | — |
 Alston Observatory | Reino Unido | Longridge | — |
| Alt emporda Observatory | España | Urdanta | — |
| Altamira observatory | Canarias | Aguerche | — |
| Altdorf Observatory | Alemania | Altorf | — |
 Alte Sternwarte | Alemania | Stadtbezirk Bonn | — |
 Alte Sternwarte | Alemania | Münster | — |
| Altenburg observatory | Alemania | Altemburgo | — |
| Alter Satzberg observatory | Austria | Viena | — |
| Althuraya Astronomy Center | Emiratos Árabes Unidos | Dubái | — |
| Altimira observatory | Estados Unidos | Coto de Caza | — |
 Altitude SEE Test European Platform | Francia | — | 2.252 m |
| Alto Turia astronomical center | España | — | — |
| Altrincham observatory | Reino Unido | Trafford | — |
| Altschwendt observatory | Austria | Altschwendt | — |