M55
NGC 6809 · Globular cluster in Sagittarius
- Magnitude
- 6.3
- Size
- 19′
- Effective surface brightness
- 21.1 mag/arcsec²
- Best months
- Jun, Jul, Aug
- Declination
- -31°
- Filter
- None (broadband target)
A large, loose globular that resolves easily but sits low for northern imagers.
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 | 44% | 6 min39 subs | 9 min57 subs | 22 min133 subs |
| ZWO Seestar S50 Pro10 s subs | 23% | 7 min43 subs | 10 min62 subs | 24 min145 subs |
| ZWO Seestar S3010 s subs | 26% | 7 min43 subs | 10 min60 subs | 23 min137 subs |
| ZWO Seestar S30 Pro10 s subs | 14% | 8 min46 subs | 11 min66 subs | 25 min153 subs |
| DwarfLab DWARF 315 s subs | 19% | 9 min36 subs | 13 min54 subs | 33 min133 subs |
| DwarfLab DWARF mini15 s subs | 26% | 8 min30 subs | 9 min38 subs | 22 min89 subs |
| DwarfLab Draco30 s subs | 25% | 15 min30 subs | 15 min30 subs | 18 min37 subs |
| DwarfLab DWARF II15 s subs | 18% | 26 min103 subs | 34 min135 subs | 1 h 09 min277 subs |
| Vaonis Vespera II10 s subs | 22% | 6 min39 subs | 9 min57 subs | 22 min133 subs |
| Vaonis Vespera Pro10 s subs | 20% | 15 min92 subs | 21 min128 subs | 48 min290 subs |
| Vaonis Vespera 310 s subs | 22% | 6 min37 subs | 9 min54 subs | 21 min128 subs |
| Vaonis Vespera Pro 210 s subs | 19% | 14 min87 subs | 20 min122 subs | 46 min277 subs |
| Unistellar eQuinox 24 s subs | 56% | 7 min112 subs | 9 min139 subs | 17 min258 subs |
| Unistellar Odyssey4 s subs | 56% | 38 min565 subs | 44 min664 subs | 1 h 13 min1,099 subs |
| Celestron Origin10 s subs | 37% | 5 min30 subs | 5 min30 subs | 6 min37 subs |
| Celestron Origin Mark II10 s subs | 42% | 5 min30 subs | 5 min30 subs | 8 min51 subs |
Imaging the globular cluster
Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.
Per-telescope pages
- How long to image the M55 with the ZWO Seestar S50
- How long to image the M55 with the ZWO Seestar S50 Pro
- How long to image the M55 with the ZWO Seestar S30
- How long to image the M55 with the ZWO Seestar S30 Pro
- How long to image the M55 with the DwarfLab DWARF 3
- How long to image the M55 with the DwarfLab DWARF mini
- How long to image the M55 with the DwarfLab Draco
- How long to image the M55 with the DwarfLab DWARF II
- How long to image the M55 with the Vaonis Vespera II
- How long to image the M55 with the Vaonis Vespera Pro
- How long to image the M55 with the Vaonis Vespera 3
- How long to image the M55 with the Vaonis Vespera Pro 2
- How long to image the M55 with the Unistellar eQuinox 2
- How long to image the M55 with the Unistellar Odyssey
- How long to image the M55 with the Celestron Origin
- How long to image the M55 with the Celestron Origin Mark II