Whale Galaxy

NGC 4631, Caldwell 32 · Galaxy in Canes Venatici

Magnitude: 9.2
Size: 15.5′ × 2.7′
Effective surface brightness: 21.9 mag/arcsec²
Best months: Mar, Apr, May
Declination: +33°
Filter: None (broadband target)

A distorted edge-on galaxy with a small companion on its back, and the Hockey Stick (NGC 4656) in the same wide field.

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 Whale Galaxy, default sub length, recommended filter, and how much of each frame it fills. Click a cell for the full Bortle 1 to 9 table.
Telescope	In frame	Bortle 3 (rural)	Bortle 5 (suburban)	Bortle 7 (urban edge)
ZWO Seestar S5010 s subs	36%	22 min132 subs	35 min210 subs	1 h 32 min551 subs
ZWO Seestar S50 Pro10 s subs	19%	24 min147 subs	38 min231 subs	1 h 40 min600 subs
ZWO Seestar S3010 s subs	22%	25 min148 subs	38 min226 subs	1 h 34 min567 subs
ZWO Seestar S30 Pro10 s subs	12%	26 min157 subs	41 min246 subs	1 h 46 min634 subs
DwarfLab DWARF 315 s subs	16%	29 min117 subs	49 min197 subs	2 h 17 min548 subs
DwarfLab DWARF mini15 s subs	22%	22 min87 subs	35 min139 subs	1 h 32 min367 subs
DwarfLab Draco30 s subs	21%	18 min36 subs	28 min57 subs	1 h 16 min152 subs
DwarfLab DWARF II15 s subs	14%	1 h 35 min381 subs	2 h 11 min526 subs	4 h 49 min1,157 subs
Vaonis Vespera II10 s subs	18%	22 min132 subs	35 min210 subs	1 h 32 min551 subs
Vaonis Vespera Pro10 s subs	16%	53 min321 subs	1 h 21 min485 subs	3 h 20 min1,202 subs
Vaonis Vespera 310 s subs	18%	21 min125 subs	33 min200 subs	1 h 28 min528 subs
Vaonis Vespera Pro 210 s subs	16%	50 min303 subs	1 h 17 min461 subs	3 h 11 min1,149 subs
Unistellar eQuinox 24 s subs	45%	29 min432 subs	37 min554 subs	1 h 12 min1,085 subs
Unistellar Odyssey4 s subs	46%	2 h 32 min2,285 subs	3 h 02 min2,727 subs	5 h 11 min4,660 subs
Celestron Origin10 s subs	30%	5 min32 subs	9 min54 subs	25 min151 subs
Celestron Origin Mark II10 s subs	35%	7 min40 subs	12 min72 subs	35 min211 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.

Whale Galaxy

How long with each smart telescope

Imaging the galaxy

Per-telescope pages