21028+4551
- Unique Name: 21028+4551BU 1138AC
- RA: 21 02 48.62
- Dec: +45 50 56.0
- Discoverer: BU
- Discoverer Number: 1138
- Components: AC
- First year: 1892
- Last year: 2012
- Observations: 21
- First position angle: 313
- Last position angle: 330
- First separation: 168.7
- Last separation: 152.1
- Mag first component: 6.46
- Mag second component: 7.82
- Spectral type: B8
- Primary proper motion RA: 3
- Primary proper motion DEC: -3
- Secondary proper motion RA: 404
- Secondary proper motion DEC: 141
- Durchmusterung:
- Notes: NS U
