How Many Subs

NGC 2403

Caldwell 7 · Galaxy in Camelopardalis

Magnitude
8.9
Size
21′ × 12′
Effective surface brightness
22.6 mag/arcsec²
Best months
Dec, Jan, Feb
Declination
+66°
Filter
None (broadband target)

A big, loose spiral in Camelopardalis that looks like a small M33, with bright H II regions dual-band can pick out.

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 NGC 2403, 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 subs49%1 h 11 min429 subs2 h721 subs5 h 33 min1,999 subs
ZWO Seestar S50 Pro10 s subs25%1 h 20 min478 subs2 h 12 min794 subs6 h 03 min2,177 subs
ZWO Seestar S3010 s subs29%1 h 21 min489 subs2 h 10 min781 subs5 h 43 min2,060 subs
ZWO Seestar S30 Pro10 s subs16%1 h 25 min513 subs2 h 21 min846 subs6 h 23 min2,300 subs
DwarfLab DWARF 315 s subs21%1 h 32 min368 subs2 h 47 min669 subs8 h 16 min1,985 subs
DwarfLab DWARF mini15 s subs29%1 h 10 min282 subs1 h 59 min477 subs5 h 32 min1,329 subs
DwarfLab Draco30 s subs28%57 min114 subs1 h 38 min196 subs4 h 35 min551 subs
DwarfLab DWARF II15 s subs20%5 h 26 min1,306 subs7 h 42 min1,848 subs18 h4,215 subs
Vaonis Vespera II10 s subs24%1 h 11 min429 subs2 h721 subs5 h 33 min1,999 subs
Vaonis Vespera Pro10 s subs22%2 h 57 min1,064 subs4 h 40 min1,679 subs12 h4,366 subs
Vaonis Vespera 310 s subs24%1 h 07 min405 subs1 h 54 min686 subs5 h 19 min1,914 subs
Vaonis Vespera Pro 210 s subs21%2 h 47 min1,002 subs4 h 25 min1,593 subs12 h4,174 subs
Unistellar eQuinox 24 s subs61%1 h 41 min1,516 subs2 h 11 min1,971 subs4 h 24 min3,963 subs
Unistellar Odyssey4 s subs62%9 h 06 min8,189 subs11 h9,847 subs19 h17,094 subs
Celestron Origin10 s subs41%16 min99 subs30 min182 subs1 h 31 min545 subs
Celestron Origin Mark II10 s subs47%20 min121 subs40 min240 subs2 h 07 min763 subs

Open in the calculator

Imaging the galaxy

Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.

Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.

Per-telescope pages