| Code | Description | Items |
|---|---|---|
| 520 | Astronomy & allied sciences | 84 |
| 521 | Celestial mechanics | 1 |
| 522 | Techniques, equipment, materials | 12 |
| 523 | Specific celestial bodies & phenomena | 251 |
| 525 | Earth (Astronomical geography) | 3 |
| 526 | Mathematical geography | 6 |
| 527 | Celestial navigation | 2 |
| 528 | Ephemerides | 1 |
| 529 | Chronology | 10 |