M10

NGC 6254 · Globular cluster in Ophiuchus

Magnitude: 6.6
Size: 20′
Effective surface brightness: 21.5 mag/arcsec²
Best months: May, Jun, Jul
Declination: -4°
Filter: None (broadband target)

A bright globular in Ophiuchus, three degrees from its twin M12. Both fit a short session.

Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

How long with each smart telescope

Total integration for a solid image of the M10, default sub length, recommended filter, and how much of each frame it fills. Click a cell for the full Bortle 1 to 9 table.
Telescope	In frame	Bortle 3 (rural)	Bortle 5 (suburban)	Bortle 7 (urban edge)
ZWO Seestar S5010 s subs	46%	12 min71 subs	18 min109 subs	45 min272 subs
ZWO Seestar S50 Pro10 s subs	24%	13 min79 subs	20 min119 subs	49 min296 subs
ZWO Seestar S3010 s subs	28%	13 min79 subs	19 min117 subs	47 min280 subs
ZWO Seestar S30 Pro10 s subs	15%	14 min84 subs	21 min127 subs	52 min313 subs
DwarfLab DWARF 315 s subs	20%	16 min64 subs	26 min103 subs	1 h 08 min271 subs
DwarfLab DWARF mini15 s subs	28%	12 min47 subs	18 min72 subs	45 min181 subs
DwarfLab Draco30 s subs	27%	15 min30 subs	15 min30 subs	37 min75 subs
DwarfLab DWARF II15 s subs	19%	49 min197 subs	1 h 07 min267 subs	2 h 22 min569 subs
Vaonis Vespera II10 s subs	23%	12 min71 subs	18 min109 subs	45 min272 subs
Vaonis Vespera Pro10 s subs	21%	28 min170 subs	41 min249 subs	1 h 39 min593 subs
Vaonis Vespera 310 s subs	23%	11 min68 subs	17 min104 subs	43 min261 subs
Vaonis Vespera Pro 210 s subs	20%	27 min161 subs	39 min237 subs	1 h 34 min567 subs
Unistellar eQuinox 24 s subs	58%	15 min219 subs	18 min278 subs	35 min533 subs
Unistellar Odyssey4 s subs	59%	1 h 16 min1,139 subs	1 h 30 min1,351 subs	2 h 32 min2,278 subs
Celestron Origin10 s subs	39%	5 min30 subs	5 min30 subs	12 min75 subs
Celestron Origin Mark II10 s subs	45%	5 min30 subs	6 min38 subs	17 min105 subs

Open in the calculator

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.

M10

How long with each smart telescope

Imaging the globular cluster

Per-telescope pages