How Many Subs

M99

NGC 4254, Coma Pinwheel · Galaxy in Coma Berenices

Magnitude
9.9
Size
5.4′ × 4.8′
Effective surface brightness
22.1 mag/arcsec²
Best months
Mar, Apr, May
Declination
+14°
Filter
None (broadband target)

A face-on spiral with one arm flung out by an encounter. Small but distinctive.

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 M99, 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 subs13%1 h 06 min396 subs1 h 47 min641 subs4 h 45 min1,709 subs
ZWO Seestar S50 Pro10 s subs7%1 h 13 min440 subs1 h 57 min705 subs5 h 10 min1,861 subs
ZWO Seestar S3010 s subs8%1 h 14 min446 subs1 h 55 min691 subs4 h 53 min1,760 subs
ZWO Seestar S30 Pro10 s subs4%1 h 19 min472 subs2 h 05 min750 subs5 h 28 min1,966 subs
DwarfLab DWARF 315 s subs5%1 h 26 min346 subs2 h 29 min598 subs7 h 05 min1,699 subs
DwarfLab DWARF mini15 s subs8%1 h 05 min261 subs1 h 46 min424 subs4 h 44 min1,137 subs
DwarfLab Draco30 s subs7%53 min106 subs1 h 27 min174 subs3 h 55 min471 subs
DwarfLab DWARF II15 s subs5%4 h 50 min1,162 subs6 h 44 min1,615 subs15 h3,594 subs
Vaonis Vespera II10 s subs6%1 h 06 min396 subs1 h 47 min641 subs4 h 45 min1,709 subs
Vaonis Vespera Pro10 s subs6%2 h 41 min968 subs4 h 07 min1,482 subs10 h3,729 subs
Vaonis Vespera 310 s subs6%1 h 02 min375 subs1 h 42 min610 subs4 h 33 min1,636 subs
Vaonis Vespera Pro 210 s subs5%2 h 32 min914 subs3 h 55 min1,408 subs9 h 54 min3,566 subs
Unistellar eQuinox 24 s subs16%1 h 28 min1,326 subs1 h 54 min1,707 subs3 h 45 min3,372 subs
Unistellar Odyssey4 s subs16%7 h 51 min7,060 subs9 h 23 min8,446 subs16 h14,505 subs
Celestron Origin10 s subs11%16 min94 subs27 min163 subs1 h 18 min466 subs
Celestron Origin Mark II10 s subs12%19 min117 subs36 min217 subs1 h 49 min653 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