| Abbreviation | Definition |
|---|---|
| BLO | Bl Lac Object |
| BLOB | Binary Large Object |
| BM | Blue Moon |
| BMAA | Bucks Mont Astronomical Association |
| BMO | Black Moving Object |
| BNCA | Belgian National Committee for Astronomy |
| BO | Biological Origin |
| BOAO | Bohyunsan Optical Astronomy Observatory |
| BOOK | Bio Optical Organized Knowledge |
| BOSS | Bullet Of Super Speed |
| BPA | Board on Physics and Astronomy |
| BRAS | Baton Rouge Astronomical Society |
| BS | Bica and Schmitt |
| BS | Burrell Schmidt telescope |
| BSAS | Barnard Seyfert Astronomical Society |
| BST | British Summer Time [GMT + 0100] |
| B-V | Binary - Variable star |
| BVAC | Brazos Valley Astronomy Club |
| BZ | Brillouin zone - a uniquely defined primitive cell in reciprocal space |
| CAA | Committee on Astronomy and Astrophysics |