Pinwheel Galaxy

M101, NGC 5457 · Galaxy in Ursa Major

Magnitude: 7.9
Size: 29′ × 27′
Effective surface brightness: 22.8 mag/arcsec²
Best months: Apr, May, Jun
Declination: +54°
Filter: None (broadband target)

Big, face-on and faint. Its total magnitude is flattering; spread over half a degree the arms are dim and demand hours, especially from suburban skies.

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 Pinwheel 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	67%	1 h 40 min602 subs	2 h 51 min1,025 subs	7 h 59 min2,873 subs
ZWO Seestar S50 Pro10 s subs	35%	1 h 52 min672 subs	3 h 08 min1,129 subs	8 h 41 min3,128 subs
ZWO Seestar S3010 s subs	40%	1 h 55 min689 subs	3 h 05 min1,112 subs	8 h 13 min2,960 subs
ZWO Seestar S30 Pro10 s subs	22%	2 h722 subs	3 h 20 min1,203 subs	9 h 11 min3,306 subs
DwarfLab DWARF 315 s subs	29%	2 h 08 min514 subs	3 h 57 min949 subs	12 h2,852 subs
DwarfLab DWARF mini15 s subs	40%	1 h 39 min396 subs	2 h 49 min678 subs	7 h 57 min1,910 subs
DwarfLab Draco30 s subs	39%	1 h 20 min160 subs	2 h 19 min278 subs	6 h 35 min791 subs
DwarfLab DWARF II15 s subs	27%	7 h 44 min1,856 subs	11 h2,639 subs	25 h6,061 subs
Vaonis Vespera II10 s subs	34%	1 h 40 min602 subs	2 h 51 min1,025 subs	7 h 59 min2,873 subs
Vaonis Vespera Pro10 s subs	30%	4 h 10 min1,501 subs	6 h 38 min2,390 subs	17 h6,275 subs
Vaonis Vespera 310 s subs	33%	1 h 35 min569 subs	2 h 42 min975 subs	7 h 38 min2,750 subs
Vaonis Vespera Pro 210 s subs	29%	3 h 56 min1,414 subs	6 h 18 min2,267 subs	17 h5,998 subs
Unistellar eQuinox 24 s subs	85%	2 h 24 min2,164 subs	3 h 08 min2,823 subs	6 h 20 min5,702 subs
Unistellar Odyssey4 s subs	86%	13 h11,739 subs	16 h14,136 subs	27 h24,611 subs
Celestron Origin10 s subs	57%	23 min138 subs	43 min258 subs	2 h 10 min782 subs
Celestron Origin Mark II10 s subs	65%	28 min168 subs	57 min340 subs	3 h 02 min1,095 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.

Pinwheel Galaxy

How long with each smart telescope

Imaging the galaxy

Per-telescope pages