How Many Subs

Cocoon Nebula

IC 5146, Caldwell 19 · Emission nebula in Cygnus

Magnitude
7.2
Size
12′
Effective surface brightness
22.7 mag/arcsec²
Best months
Jul, Aug, Sep
Declination
+47°
Filter
Dual-band recommended

A round emission and reflection nebula at the end of a long dark lane. Mixed light, so a broadband stack keeps the blue.

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 Cocoon 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-band28%2 h 02 min731 subs2 h 24 min866 subs4 h 02 min1,454 subs
ZWO Seestar S50 Pro10 s subs, dual-band14%2 h 19 min835 subs2 h 43 min981 subs4 h 29 min1,617 subs
ZWO Seestar S3010 s subs, dual-band17%2 h 33 min916 subs2 h 55 min1,051 subs4 h 33 min1,639 subs
ZWO Seestar S30 Pro10 s subs, dual-band9%2 h 32 min911 subs2 h 57 min1,064 subs4 h 49 min1,733 subs
DwarfLab DWARF 315 s subs, dual-band12%2 h 12 min528 subs2 h 46 min666 subs5 h 18 min1,272 subs
DwarfLab DWARF mini15 s subs, dual-band17%1 h 59 min476 subs2 h 21 min566 subs3 h 59 min958 subs
DwarfLab Draco30 s subs, dual-band16%1 h 34 min188 subs1 h 52 min225 subs3 h 14 min389 subs
DwarfLab DWARF II15 s subs11%8 h 06 min1,946 subs11 h2,760 subs26 h6,317 subs
Vaonis Vespera II10 s subs14%1 h 46 min635 subs2 h 59 min1,074 subs8 h 19 min2,995 subs
Vaonis Vespera Pro10 s subs12%4 h 23 min1,579 subs6 h 57 min2,503 subs18 h6,542 subs
Vaonis Vespera 310 s subs14%1 h 40 min600 subs2 h 50 min1,022 subs7 h 58 min2,867 subs
Vaonis Vespera Pro 210 s subs12%4 h 08 min1,487 subs6 h 36 min2,375 subs17 h6,254 subs
Unistellar eQuinox 24 s subs35%2 h 31 min2,263 subs3 h 17 min2,948 subs6 h 36 min5,941 subs
Unistellar Odyssey4 s subs36%14 h12,254 subs16 h14,745 subs28 h25,636 subs
Celestron Origin10 s subs23%24 min146 subs45 min271 subs2 h 16 min816 subs
Celestron Origin Mark II10 s subs27%30 min178 subs59 min357 subs3 h 10 min1,142 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