How Many Subs

Lagoon Nebula

M8, NGC 6523 · Emission nebula in Sagittarius

Magnitude
6.0
Size
90′ × 40′
Effective surface brightness
21.5 mag/arcsec²
Best months
Jun, Jul, Aug
Declination
-24°
Filter
Dual-band recommended

The showpiece emission nebula of the summer Milky Way, bright enough to catch its core in minutes. Pair it with the Trifid in one wide frame.

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 Lagoon Nebula, default sub length, recommended filter, and how much of each frame it fills. Click a cell for the full Bortle 1 to 9 table.
TelescopeIn frameBortle 3 (rural)Bortle 5 (suburban)Bortle 7 (urban edge)
ZWO Seestar S5010 s subs, dual-band2.1× frame15 min89 subs17 min101 subs25 min152 subs
ZWO Seestar S50 Pro10 s subs, dual-band1.1× frame17 min100 subs19 min113 subs28 min169 subs
ZWO Seestar S3010 s subs, dual-band1.3× frame17 min105 subs19 min117 subs28 min169 subs
ZWO Seestar S30 Pro10 s subs, dual-band67%18 min108 subs20 min122 subs30 min180 subs
DwarfLab DWARF 315 s subs, dual-bandOnly just18 min72 subs21 min84 subs34 min137 subs
DwarfLab DWARF mini15 s subs, dual-band1.3× frame14 min58 subs16 min66 subs25 min101 subs
DwarfLab Draco30 s subs, dual-band1.2× frame15 min30 subs15 min30 subs20 min41 subs
DwarfLab DWARF II15 s subs84%51 min203 subs1 h 08 min274 subs2 h 26 min586 subs
Vaonis Vespera II10 s subs1.0× frame12 min73 subs19 min112 subs47 min280 subs
Vaonis Vespera Pro10 s subsOnly just29 min175 subs43 min256 subs1 h 42 min610 subs
Vaonis Vespera 310 s subs1.0× frame11 min69 subs18 min106 subs45 min268 subs
Vaonis Vespera Pro 210 s subsOnly just27 min165 subs40 min243 subs1 h 37 min583 subs
Unistellar eQuinox 24 s subs2.6× frame15 min226 subs19 min286 subs37 min548 subs
Unistellar Odyssey4 s subs2.7× frame1 h 18 min1,172 subs1 h 33 min1,391 subs2 h 36 min2,346 subs
Celestron Origin10 s subs1.8× frame5 min30 subs5 min30 subs13 min77 subs
Celestron Origin Mark II10 s subs2.0× frame5 min30 subs6 min39 subs18 min108 subs

Open in the calculator

Imaging the emission nebula

Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.

Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.

Per-telescope pages