| Abbreviation | Definition |
|---|---|
| AAA | Amateur Astronomers Association |
| AAAA | Asociación Argentina Amigos de la Astronomía |
| AAAD | Amateur Astronomers Association Delhi |
| AAAD | Amateur Astronomers Association of Delhi |
| AAAM | Active Amateur Astronomers of Maryland |
| AAG | Amateur Astronomy Group |
| AAJ | Astronomical Association of Jamaica |
| AAL | Astronomy Associates of Lawrence |
| AAL | Astronomy Associates of Lawrence Astronomy Associates of Lawrence |
| AAPF | Astronomy and Astrophysics Postdoctoral Fellowships |
| AAS | American Astronautical Society |
| AAS | Archaeology, Astronautics, and Seti |
| AASC | Astronomy and Astrophysics Survey Committee |
| AASI | Astronomical Association of Southern Illinois |
| AAT | Anglo Australian Telescope |
| AAV | Astronomical Analogue Video |
| AAVSO | American Association of Variable Star Observers |
| ABB | After the Big Bang |
| ABBA | ADC Backend For Bolometer Array |
| ABF | Astronomische Beeldverwerkings Faciliteiten |