How Many Subs

Triangulum Galaxy

M33, NGC 598 · Galaxy in Triangulum

Magnitude
5.7
Size
73′ × 45′
Effective surface brightness
22.5 mag/arcsec²
Best months
Sep, Oct, Nov
Declination
+31°
Filter
None (broadband target)

Big, face-on and low in surface brightness. Nearly as bright as M31 overall but spread thin, so it needs far more time. Its H II regions pop with a dual-band filter.

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 Triangulum Galaxy, default sub length, recommended filter. Click a cell for the full Bortle 1 to 9 table.
TelescopeBortle 3 (rural)Bortle 5 (suburban)Bortle 7 (urban edge)
ZWO Seestar S5010 s subs1 h 24 min505 subs2 h 05 min748 subs5 h 02 min1,811 subs
ZWO Seestar S50 Pro10 s subs1 h 07 min404 subs1 h 51 min667 subs5 h 03 min1,817 subs
ZWO Seestar S3010 s subs1 h362 subs1 h 41 min605 subs4 h 38 min1,669 subs
ZWO Seestar S30 Pro10 s subs1 h 12 min433 subs1 h 58 min710 subs5 h 20 min1,920 subs
DwarfLab Dwarf 315 s subs1 h 37 min389 subs2 h 40 min640 subs7 h 14 min1,735 subs
DwarfLab Dwarf Mini15 s subs54 min216 subs1 h 34 min378 subs4 h 32 min1,087 subs
DwarfLab Dwarf II15 s subs4 h 34 min1,097 subs6 h 27 min1,548 subs15 h3,516 subs
Vaonis Vespera II10 s subs1 h362 subs1 h 41 min605 subs4 h 38 min1,669 subs
Vaonis Vespera Pro10 s subs2 h 60 min1,078 subs4 h 25 min1,589 subs11 h3,825 subs
Unistellar eQuinox 24 s subs1 h 25 min1,270 subs1 h 50 min1,649 subs3 h 40 min3,305 subs
Unistellar Odyssey4 s subs7 h 36 min6,843 subs9 h 08 min8,222 subs16 h14,250 subs
Celestron Origin10 s subs14 min84 subs25 min153 subs1 h 16 min455 subs

Open in the calculator

Imaging the galaxy

Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.

Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.

Per-telescope pages