| Abbreviation | Definition |
|---|---|
| LMST | Local Mean Sidereal Time |
| LMT | Large Millimeter Telescope |
| LOAO | Lemmon Optical Astronomy Observatory |
| LOAO | Lemmonsan Optical Astronomical Observatory |
| LOAO | Lemmonsan Optical Astronomy Observatory |
| LOD | Length Of Day |
| LOESS | Lincoln Orbit Earth Science Society |
| LOFAR | Low-Frequency Array |
| LOSS | Lick Observatory Supernova Search |
| LP | Lonely Planet |
| LPAO | La Plata Astronomical Observatory |
| LPC | Long Period Comets |
| LPCI | Lunar Phases Concept Inventory |
| LR | Long Radius |
| LRBO | Launcher Rockets and Balloon Operations |
| LS | List Star |
| LSB | Low Surface Brightness |
| LSST | Large Synoptic Survey Telescope |
| LST | Local Sidereal Time |
| LSVT | Large Solar Vacuum Telescope |