How Many Subs

North America Nebula

NGC 7000, Caldwell 20 · Emission nebula in Cygnus

Magnitude
4.0
Size
120′ × 100′
Effective surface brightness
22.4 mag/arcsec²
Best months
Jul, Aug, Sep
Declination
+44°
Filter
Dual-band recommended

A huge emission cloud next to Deneb shaped like the continent. The Cygnus Wall is the bright bit; a dual-band filter and a wide field make it one of the best summer targets from town.

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 North America 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-band2.8× frame59 min357 subs1 h 10 min419 subs1 h 55 min690 subs
ZWO Seestar S50 Pro10 s subs, dual-band1.4× frame1 h 08 min407 subs1 h 19 min474 subs2 h 08 min766 subs
ZWO Seestar S3010 s subs, dual-band1.7× frame1 h 14 min442 subs1 h 24 min504 subs2 h 09 min775 subs
ZWO Seestar S30 Pro10 s subs, dual-band89%1 h 14 min443 subs1 h 25 min513 subs2 h 17 min821 subs
DwarfLab DWARF 315 s subs, dual-band1.2× frame1 h 06 min264 subs1 h 22 min328 subs2 h 32 min607 subs
DwarfLab DWARF mini15 s subs, dual-band1.7× frame58 min233 subs1 h 08 min274 subs1 h 54 min455 subs
DwarfLab Draco30 s subs, dual-band1.6× frame46 min92 subs55 min110 subs1 h 32 min185 subs
DwarfLab DWARF II15 s subs1.1× frame3 h 50 min922 subs5 h 24 min1,297 subs12 h2,934 subs
Vaonis Vespera II10 s subs1.4× frame51 min306 subs1 h 25 min509 subs3 h 52 min1,393 subs
Vaonis Vespera Pro10 s subs1.2× frame2 h 06 min757 subs3 h 17 min1,182 subs8 h 27 min3,041 subs
Vaonis Vespera 310 s subs1.4× frame48 min290 subs1 h 21 min484 subs3 h 42 min1,334 subs
Vaonis Vespera Pro 210 s subs1.2× frame1 h 59 min713 subs3 h 07 min1,122 subs8 h 05 min2,908 subs
Unistellar eQuinox 24 s subs3.5× frame1 h 11 min1,064 subs1 h 32 min1,379 subs3 h 04 min2,757 subs
Unistellar Odyssey4 s subs3.6× frame6 h 21 min5,721 subs7 h 38 min6,868 subs13 h11,882 subs
Celestron Origin10 s subs2.3× frame12 min72 subs21 min129 subs1 h 03 min380 subs
Celestron Origin Mark II10 s subs2.7× frame15 min88 subs28 min171 subs1 h 29 min532 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