How Many Subs

ZWO Seestar S50: how long to image deep-sky targets

The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.

SpecValue
Aperture50 mm
Focal length250 mm (f/5.0)
SensorSony IMX462, 1920 × 1080, 2.9 µm pixels
Pixel scale2.39″ per pixel
Field of view1.28° × 0.72° (77′ × 43′)
Sub exposures10 s, 20 s, 30 s, 60 s (default 10 s)
FiltersBuilt-in dual-band light-pollution filter, switchable in the app. What the names mean.
In the calculator“UV/IR-cut (no light-pollution filter)” is the UV/IR-cut position; “dual-band” is the built-in dual-band (LP filter).
Read noise used1 e⁻
Where to buy the Seestar S50ZWO store DirectAmazon UKAmazon USThe ZWO store link is a plain link; the others are affiliate links. As an Amazon Associate I earn from qualifying purchases, at no cost to you.

Weighing it against the others? The buying guide puts every scope on one table.

Popular targets

Total integration for a solid image, 10 s subs, recommended filter.
TargetBortle 4Bortle 6Bortle 8
Andromeda GalaxyGalaxy42 min254 subs1 h 27 min525 subs4 h 04 min1,465 subs
Orion NebulaEmission nebula, dual-band10 min61 subs12 min75 subs21 min125 subs
PleiadesReflection nebula1 h 16 min456 subs2 h 42 min971 subs7 h 38 min2,751 subs
Whirlpool GalaxyGalaxy29 min177 subs59 min352 subs2 h 39 min955 subs
Bode's GalaxyGalaxy31 min188 subs1 h 04 min383 subs2 h 56 min1,056 subs
Pinwheel GalaxyGalaxy2 h 08 min766 subs4 h 37 min1,661 subs13 h4,754 subs
Hercules ClusterGlobular cluster5 min30 subs7 min44 subs18 min107 subs
Dumbbell NebulaPlanetary nebula, dual-band16 min99 subs20 min121 subs33 min198 subs
Ring NebulaPlanetary nebula, dual-band6 min37 subs7 min42 subs10 min60 subs
Lagoon NebulaEmission nebula, dual-band16 min94 subs20 min119 subs34 min205 subs
Eagle NebulaEmission nebula, dual-band46 min275 subs1 h 01 min366 subs1 h 53 min680 subs
Omega NebulaEmission nebula, dual-band18 min110 subs23 min138 subs39 min236 subs
Trifid NebulaEmission nebula, dual-band33 min200 subs44 min263 subs1 h 20 min480 subs
Triangulum GalaxyGalaxy1 h 16 min456 subs2 h 42 min971 subs7 h 38 min2,751 subs
North America NebulaEmission nebula, dual-band1 h 03 min381 subs1 h 25 min512 subs2 h 41 min965 subs
Western Veil NebulaSupernova remnant, dual-band1 h 09 min414 subs1 h 33 min557 subs2 h 56 min1,054 subs
Eastern Veil NebulaSupernova remnant, dual-band58 min351 subs1 h 18 min471 subs2 h 27 min884 subs
Elephant's Trunk NebulaEmission nebula, dual-band1 h 44 min627 subs2 h 22 min855 subs4 h 34 min1,642 subs
Iris NebulaReflection nebula54 min325 subs1 h 53 min681 subs5 h 19 min1,913 subs
Pacman NebulaEmission nebula, dual-band1 h 15 min449 subs1 h 41 min607 subs3 h 12 min1,152 subs
Heart NebulaEmission nebula, dual-band2 h 04 min742 subs2 h 49 min1,016 subs5 h 27 min1,963 subs
Rosette NebulaEmission nebula, dual-band1 h 03 min381 subs1 h 25 min512 subs2 h 41 min965 subs
Horsehead NebulaEmission nebula, dual-band1 h 28 min530 subs2 h720 subs3 h 49 min1,375 subs
Flame NebulaEmission nebula, dual-band24 min147 subs32 min190 subs57 min340 subs
California NebulaEmission nebula, dual-band1 h 28 min530 subs2 h720 subs3 h 49 min1,375 subs
Helix NebulaPlanetary nebula, dual-band1 h 28 min530 subs2 h720 subs3 h 49 min1,375 subs
Double ClusterOpen cluster5 min30 subs5 min30 subs6 min34 subs
NGC 891Galaxy1 h 17 min465 subs2 h 44 min986 subs7 h 44 min2,787 subs
Sombrero GalaxyGalaxy24 min146 subs47 min283 subs2 h 05 min753 subs
Sunflower GalaxyGalaxy48 min287 subs1 h 39 min593 subs4 h 35 min1,651 subs

All 170 targets have a page for the Seestar S50.

Every target for the Seestar S50

Supernova remnants

Globular clusters

Open clusters

Emission nebulas

Star clouds

Planetary nebulas

Galaxies

Reflection nebulas

Getting the most from the Seestar S50

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.

Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 s and 60 s subs is small; from a rural site it can halve the total time, especially with a dual-band filter in place.

Stack across nights. Every smart scope app can continue a stack or you can combine the saved frames on a computer; the figures here are totals, not single-session limits.

Compare the Seestar S50

Useful gear

What actually fits this scope, checked against the maker's own pages: power, EQ mode, dew and carry.

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All Seestar S50 accessories, and what to take on a cold night →