21028+4551
- Unique Name: 21028+4551BU 1138AB
- RA: 21 02 48.62
- Dec: +45 50 56.0
- Discoverer: BU
- Discoverer Number: 1138
- Components: AB
- First year: 1888
- Last year: 2006
- Observations: 57
- First position angle: 186
- Last position angle: 172
- First separation: 0.3
- Last separation: 0.1
- Mag first component: 7.1
- Mag second component: 7.3
- Spectral type: B3Vn
- Primary proper motion RA: 9
- Primary proper motion DEC: 4
- Secondary proper motion RA:
- Secondary proper motion DEC:
- Durchmusterung: +45 3374
- Notes: NO
