| WDS ID | 21435+5847 |
| Common catalogue ID | BU 690 |
| Components | AB |
| Other Designation | mu Cep (Erakis: Herschel's Garnet Star) |
| Position angle | 259 |
| Separation | 19.3 |
| Mag First | 4.27 |
| Mag Second | 12.3 |
| Delta mag | 8.03 |
| Spectral Type | M2Iae+K2II |
| Constellation | Cepheus |
| RA | 21:43:30.4 |
| Dec | +58:46:48.2 |