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 30 s.
| Spec | Value |
|---|---|
| Aperture | 50 mm |
| Focal length | 250 mm (f/5.0) |
| Sensor | Sony IMX462, 1920 × 1080, 2.9 µm pixels |
| Pixel scale | 2.39″ per pixel |
| Field of view | 1.28° × 0.72° (77′ × 43′) |
| Sub exposures | 10 s, 20 s, 30 s (default 10 s) |
| Filter | Built-in dual-band light-pollution filter, switchable in the app. |
| Read noise used | 1.5 e⁻ |
Popular targets
| Target | Bortle 4 | Bortle 6 | Bortle 8 |
|---|---|---|---|
| Andromeda GalaxyGalaxy | 55 min329 subs | 1 h 40 min601 subs | 4 h 17 min1,540 subs |
| Orion NebulaEmission nebula, dual-band | 14 min87 subs | 17 min102 subs | 25 min151 subs |
| PleiadesReflection nebula | 1 h 40 min599 subs | 3 h 06 min1,114 subs | 8 h 02 min2,894 subs |
| Whirlpool GalaxyGalaxy | 37 min225 subs | 1 h 07 min400 subs | 2 h 47 min1,004 subs |
| Bode's GalaxyGalaxy | 40 min242 subs | 1 h 13 min437 subs | 3 h 05 min1,110 subs |
| Pinwheel GalaxyGalaxy | 2 h 49 min1,013 subs | 5 h 18 min1,908 subs | 14 h5,001 subs |
| Hercules ClusterGlobular cluster | 5 min31 subs | 8 min49 subs | 19 min112 subs |
| Dumbbell NebulaPlanetary nebula, dual-band | 23 min140 subs | 27 min162 subs | 40 min240 subs |
| Ring NebulaPlanetary nebula, dual-band | 8 min46 subs | 8 min51 subs | 11 min69 subs |
| Lagoon NebulaEmission nebula, dual-band | 23 min140 subs | 27 min165 subs | 42 min251 subs |
| Eagle NebulaEmission nebula, dual-band | 1 h 14 min443 subs | 1 h 29 min533 subs | 2 h 21 min847 subs |
| Omega NebulaEmission nebula, dual-band | 20 min119 subs | 23 min140 subs | 35 min212 subs |
| Trifid NebulaEmission nebula, dual-band | 53 min316 subs | 1 h 03 min379 subs | 1 h 39 min596 subs |
| Triangulum GalaxyGalaxy | 1 h 40 min599 subs | 3 h 06 min1,114 subs | 8 h 02 min2,894 subs |
| North America NebulaEmission nebula, dual-band | 1 h 44 min623 subs | 2 h 06 min754 subs | 3 h 21 min1,207 subs |
| Western Veil NebulaSupernova remnant, dual-band | 1 h 53 min679 subs | 2 h 17 min823 subs | 3 h 40 min1,319 subs |
| Eastern Veil NebulaSupernova remnant, dual-band | 1 h 35 min572 subs | 1 h 55 min691 subs | 3 h 04 min1,105 subs |
| Elephant's Trunk NebulaEmission nebula, dual-band | 2 h 54 min1,047 subs | 3 h 32 min1,275 subs | 5 h 44 min2,062 subs |
| Iris NebulaReflection nebula | 1 h 10 min423 subs | 2 h 10 min780 subs | 5 h 35 min2,011 subs |
| Pacman NebulaEmission nebula, dual-band | 2 h 03 min740 subs | 2 h 30 min898 subs | 4 h1,442 subs |
| Heart NebulaEmission nebula, dual-band | 3 h 28 min1,247 subs | 4 h 13 min1,521 subs | 6 h 51 min2,468 subs |
| Rosette NebulaEmission nebula, dual-band | 1 h 44 min623 subs | 2 h 06 min754 subs | 3 h 21 min1,207 subs |
| Horsehead NebulaEmission nebula, dual-band | 2 h 27 min880 subs | 2 h 58 min1,069 subs | 4 h 47 min1,724 subs |
| Flame NebulaEmission nebula, dual-band | 38 min227 subs | 45 min270 subs | 1 h 10 min420 subs |
| California NebulaEmission nebula, dual-band | 2 h 27 min880 subs | 2 h 58 min1,069 subs | 4 h 47 min1,724 subs |
| Helix NebulaPlanetary nebula, dual-band | 2 h 27 min880 subs | 2 h 58 min1,069 subs | 4 h 47 min1,724 subs |
| Double ClusterOpen cluster | 5 min30 subs | 5 min30 subs | 6 min35 subs |
| NGC 891Galaxy | 1 h 41 min609 subs | 3 h 08 min1,130 subs | 8 h 08 min2,931 subs |
| Sombrero GalaxyGalaxy | 31 min184 subs | 53 min320 subs | 2 h 12 min790 subs |
| Sunflower GalaxyGalaxy | 1 h 02 min372 subs | 1 h 53 min678 subs | 4 h 49 min1,735 subs |
All 170 targets have a page for the Seestar S50.
Getting the most from the Seestar S50
20 s and 30 s subs need EQ mode (app 2.4+). 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 30 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.
Useful gear
Power, dew control and a stable tripod are what stop a long session early. Search links, not specific endorsements; check fit for your model.