How Many Subs

California Nebula

NGC 1499 · Emission nebula in Perseus

Magnitude
5.0
Size
160′ × 40′
Effective surface brightness
22.6 mag/arcsec²
Best months
Nov, Dec, Jan
Declination
+36°
Filter
Dual-band recommended

A long, faint hydrogen streak near Menkib, nearly three degrees end to end. Needs a wide field and a dual-band filter; it is almost invisible in broadband.

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 California Nebula, 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 subs, dual-band2 h 21 min845 subs2 h 36 min935 subs3 h 41 min1,326 subs
ZWO Seestar S50 Pro10 s subs, dual-band1 h 34 min566 subs1 h 50 min662 subs3 h 01 min1,086 subs
ZWO Seestar S3010 s subs, dual-band1 h 23 min496 subs1 h 37 min585 subs2 h 43 min976 subs
ZWO Seestar S30 Pro10 s subs, dual-band1 h 43 min616 subs1 h 60 min718 subs3 h 14 min1,163 subs
DwarfLab Dwarf 315 s subs, dual-band2 h 17 min550 subs2 h 40 min642 subs4 h 21 min1,045 subs
DwarfLab Dwarf Mini15 s subs, dual-band1 h 07 min268 subs1 h 22 min328 subs2 h 27 min589 subs
DwarfLab Dwarf II15 s subs5 h 26 min1,306 subs7 h 42 min1,848 subs18 h4,215 subs
Vaonis Vespera II10 s subs1 h 11 min429 subs2 h721 subs5 h 33 min1,999 subs
Vaonis Vespera Pro10 s subs3 h 34 min1,282 subs5 h 16 min1,897 subs13 h4,584 subs
Unistellar eQuinox 24 s subs1 h 41 min1,516 subs2 h 11 min1,971 subs4 h 24 min3,963 subs
Unistellar Odyssey4 s subs9 h 06 min8,189 subs11 h9,847 subs19 h17,094 subs
Celestron Origin10 s subs16 min99 subs30 min182 subs1 h 31 min545 subs

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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) 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