How Many Subs

Elephant's Trunk Nebula

IC 1396 · Emission nebula in Cepheus

Magnitude
3.5
Size
170′ × 140′
Effective surface brightness
22.7 mag/arcsec²
Best months
Jul, Aug, Sep
Declination
+58°
Filter
Dual-band recommended

A vast, faint hydrogen cloud in Cepheus with the dark trunk winding through it. Huge, so wide scopes frame the whole thing; dual-band is essential from any lit sky.

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 Elephant's Trunk 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-band3.9× frame1 h 37 min585 subs1 h 55 min693 subs3 h 14 min1,163 subs
ZWO Seestar S50 Pro10 s subs, dual-band2.1× frame1 h 51 min668 subs2 h 11 min785 subs3 h 36 min1,294 subs
ZWO Seestar S3010 s subs, dual-band2.4× frame2 h 02 min733 subs2 h 20 min841 subs3 h 38 min1,311 subs
ZWO Seestar S30 Pro10 s subs, dual-band1.3× frame2 h 01 min729 subs2 h 22 min851 subs3 h 51 min1,387 subs
DwarfLab DWARF 315 s subs, dual-band1.7× frame1 h 45 min422 subs2 h 13 min533 subs4 h 14 min1,018 subs
DwarfLab DWARF mini15 s subs, dual-band2.4× frame1 h 35 min381 subs1 h 53 min453 subs3 h 12 min767 subs
DwarfLab Draco30 s subs, dual-band2.3× frame1 h 15 min150 subs1 h 30 min180 subs2 h 35 min311 subs
DwarfLab DWARF II15 s subs1.6× frame6 h 29 min1,557 subs9 h 12 min2,208 subs21 h5,054 subs
Vaonis Vespera II10 s subs2.0× frame1 h 25 min508 subs2 h 23 min859 subs6 h 39 min2,396 subs
Vaonis Vespera Pro10 s subs1.7× frame3 h 30 min1,263 subs5 h 34 min2,002 subs15 h5,233 subs
Vaonis Vespera 310 s subs1.9× frame1 h 20 min480 subs2 h 16 min818 subs6 h 22 min2,294 subs
Vaonis Vespera Pro 210 s subs1.7× frame3 h 18 min1,190 subs5 h 17 min1,900 subs14 h5,003 subs
Unistellar eQuinox 24 s subs5.0× frame2 h 01 min1,811 subs2 h 37 min2,359 subs5 h 17 min4,753 subs
Unistellar Odyssey4 s subs5.1× frame11 h9,803 subs13 h11,796 subs23 h20,509 subs
Celestron Origin10 s subs3.3× frame19 min117 subs36 min217 subs1 h 49 min653 subs
Celestron Origin Mark II10 s subs3.8× frame24 min142 subs48 min286 subs2 h 32 min914 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