M106

NGC 4258 · Galaxy in Canes Venatici

Magnitude: 8.4
Size: 19′ × 8′
Effective surface brightness: 22.0 mag/arcsec²
Best months: Mar, Apr, May
Declination: +47°
Filter: None (broadband target)

A big, bright spiral with anomalous red arms driven by its black hole. Dual-band brings the extra arms 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 M106, 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	44%	26 min155 subs	41 min249 subs	1 h 50 min659 subs
ZWO Seestar S50 Pro10 s subs	23%	29 min172 subs	46 min274 subs	2 h718 subs
ZWO Seestar S3010 s subs	26%	29 min175 subs	45 min268 subs	1 h 53 min679 subs
ZWO Seestar S30 Pro10 s subs	14%	31 min185 subs	49 min292 subs	2 h 06 min758 subs
DwarfLab DWARF 315 s subs	19%	34 min136 subs	58 min233 subs	2 h 44 min655 subs
DwarfLab DWARF mini15 s subs	26%	25 min102 subs	41 min165 subs	1 h 50 min439 subs
DwarfLab Draco30 s subs	25%	21 min42 subs	34 min68 subs	1 h 31 min182 subs
DwarfLab DWARF II15 s subs	18%	1 h 53 min452 subs	2 h 36 min625 subs	5 h 46 min1,385 subs
Vaonis Vespera II10 s subs	22%	26 min155 subs	41 min249 subs	1 h 50 min659 subs
Vaonis Vespera Pro10 s subs	20%	1 h 03 min378 subs	1 h 36 min575 subs	4 h1,438 subs
Vaonis Vespera 310 s subs	22%	24 min147 subs	39 min237 subs	1 h 45 min631 subs
Vaonis Vespera Pro 210 s subs	19%	59 min357 subs	1 h 31 min546 subs	3 h 49 min1,375 subs
Unistellar eQuinox 24 s subs	56%	34 min514 subs	44 min660 subs	1 h 27 min1,299 subs
Unistellar Odyssey4 s subs	56%	3 h 02 min2,727 subs	3 h 37 min3,259 subs	6 h 12 min5,585 subs
Celestron Origin10 s subs	37%	6 min37 subs	11 min64 subs	30 min180 subs
Celestron Origin Mark II10 s subs	42%	8 min46 subs	14 min85 subs	42 min252 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.

M106

How long with each smart telescope

Imaging the galaxy

Per-telescope pages