M103
NGC 581 · Open cluster in Cassiopeia
- Magnitude
- 7.4
- Size
- 6′
- Effective surface brightness
- 20.0 mag/arcsec²
- Best months
- Sep, Oct, Nov
- Declination
- +61°
- Filter
- None (broadband target)
A small, fan-shaped open cluster in Cassiopeia, the last object in Messier's own list.
Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
How long with each smart telescope
| Telescope | In frame | Bortle 3 (rural) | Bortle 5 (suburban) | Bortle 7 (urban edge) |
|---|---|---|---|---|
| ZWO Seestar S5010 s subs | 14% | 5 min30 subs | 5 min30 subs | 8 min51 subs |
| ZWO Seestar S50 Pro10 s subs | 7% | 5 min30 subs | 5 min30 subs | 9 min55 subs |
| ZWO Seestar S3010 s subs | 8% | 5 min30 subs | 5 min30 subs | 9 min52 subs |
| ZWO Seestar S30 Pro10 s subs | 4% | 5 min30 subs | 5 min31 subs | 10 min58 subs |
| DwarfLab DWARF 315 s subs | 6% | 8 min30 subs | 8 min30 subs | 13 min51 subs |
| DwarfLab DWARF mini15 s subs | 8% | 8 min30 subs | 8 min30 subs | 8 min34 subs |
| DwarfLab Draco30 s subs | 8% | 15 min30 subs | 15 min30 subs | 15 min30 subs |
| DwarfLab DWARF II15 s subs | 6% | 12 min49 subs | 15 min59 subs | 26 min104 subs |
| Vaonis Vespera II10 s subs | 7% | 5 min30 subs | 5 min30 subs | 8 min51 subs |
| Vaonis Vespera Pro10 s subs | 6% | 8 min48 subs | 10 min59 subs | 18 min110 subs |
| Vaonis Vespera 310 s subs | 7% | 5 min30 subs | 5 min30 subs | 8 min49 subs |
| Vaonis Vespera Pro 210 s subs | 6% | 8 min46 subs | 9 min57 subs | 17 min105 subs |
| Unistellar eQuinox 24 s subs | 18% | 3 min49 subs | 4 min58 subs | 6 min95 subs |
| Unistellar Odyssey4 s subs | 18% | 15 min228 subs | 17 min259 subs | 26 min395 subs |
| Celestron Origin10 s subs | 12% | 5 min30 subs | 5 min30 subs | 5 min30 subs |
| Celestron Origin Mark II10 s subs | 13% | 5 min30 subs | 5 min30 subs | 5 min30 subs |
Imaging the open cluster
Open clusters are the easiest targets in the sky. The stars are bright, so the aim is colour and tight stars rather than depth: short subs, no filter, and stop before the bright members saturate. The nominal time here gets you clean star colour; more integration only adds background stars.
Per-telescope pages
- How long to image the M103 with the ZWO Seestar S50
- How long to image the M103 with the ZWO Seestar S50 Pro
- How long to image the M103 with the ZWO Seestar S30
- How long to image the M103 with the ZWO Seestar S30 Pro
- How long to image the M103 with the DwarfLab DWARF 3
- How long to image the M103 with the DwarfLab DWARF mini
- How long to image the M103 with the DwarfLab Draco
- How long to image the M103 with the DwarfLab DWARF II
- How long to image the M103 with the Vaonis Vespera II
- How long to image the M103 with the Vaonis Vespera Pro
- How long to image the M103 with the Vaonis Vespera 3
- How long to image the M103 with the Vaonis Vespera Pro 2
- How long to image the M103 with the Unistellar eQuinox 2
- How long to image the M103 with the Unistellar Odyssey
- How long to image the M103 with the Celestron Origin
- How long to image the M103 with the Celestron Origin Mark II