ZWO Seestar S50 Pro: how long to image deep-sky targets
The S50 optics on an 8 MP IMX585 with a wider, taller field and 60 s subs in EQ mode. Same per-pixel speed as the S50, four times the pixels, and the long subs make it the better dark-site scope.
| Spec | Value |
|---|---|
| Aperture | 50 mm |
| Focal length | 260 mm (f/5.2) |
| Sensor | Sony IMX585, 3840 × 2160, 2.9 µm pixels |
| Pixel scale | 2.30″ per pixel |
| Field of view | 2.45° × 1.38° (147′ × 83′) |
| Sub exposures | 10 s, 20 s, 30 s, 60 s (default 10 s) |
| Filter | Built-in filter wheel with dual-band filter. |
| Read noise used | 1 e⁻ |
Popular targets
| Target | Bortle 4 | Bortle 6 | Bortle 8 |
|---|---|---|---|
| Andromeda GalaxyGalaxy | 47 min281 subs | 1 h 36 min575 subs | 4 h 25 min1,590 subs |
| Orion NebulaEmission nebula, dual-band | 11 min68 subs | 14 min83 subs | 23 min137 subs |
| PleiadesReflection nebula | 1 h 24 min506 subs | 2 h 57 min1,063 subs | 8 h 18 min2,988 subs |
| Whirlpool GalaxyGalaxy | 32 min195 subs | 1 h 04 min384 subs | 2 h 53 min1,037 subs |
| Bode's GalaxyGalaxy | 35 min208 subs | 1 h 10 min419 subs | 3 h 11 min1,147 subs |
| Pinwheel GalaxyGalaxy | 2 h 21 min849 subs | 5 h 03 min1,817 subs | 14 h5,163 subs |
| Hercules ClusterGlobular cluster | 5 min30 subs | 8 min48 subs | 19 min116 subs |
| Dumbbell NebulaPlanetary nebula, dual-band | 18 min110 subs | 22 min134 subs | 36 min218 subs |
| Ring NebulaPlanetary nebula, dual-band | 7 min41 subs | 8 min46 subs | 11 min65 subs |
| Lagoon NebulaEmission nebula, dual-band | 17 min105 subs | 22 min132 subs | 37 min225 subs |
| Eagle NebulaEmission nebula, dual-band | 52 min312 subs | 1 h 08 min410 subs | 2 h 05 min749 subs |
| Omega NebulaEmission nebula, dual-band | 15 min91 subs | 19 min113 subs | 32 min191 subs |
| Trifid NebulaEmission nebula, dual-band | 38 min227 subs | 49 min294 subs | 1 h 28 min529 subs |
| Triangulum GalaxyGalaxy | 1 h 24 min506 subs | 2 h 57 min1,063 subs | 8 h 18 min2,988 subs |
| North America NebulaEmission nebula, dual-band | 1 h 12 min433 subs | 1 h 36 min574 subs | 2 h 57 min1,065 subs |
| Western Veil NebulaSupernova remnant, dual-band | 1 h 18 min470 subs | 1 h 44 min625 subs | 3 h 14 min1,163 subs |
| Eastern Veil NebulaSupernova remnant, dual-band | 1 h 06 min398 subs | 1 h 28 min528 subs | 2 h 42 min975 subs |
| Elephant's Trunk NebulaEmission nebula, dual-band | 1 h 59 min713 subs | 2 h 40 min960 subs | 5 h 02 min1,812 subs |
| Iris NebulaReflection nebula | 60 min360 subs | 2 h 04 min745 subs | 5 h 46 min2,077 subs |
| Pacman NebulaEmission nebula, dual-band | 1 h 25 min510 subs | 1 h 53 min681 subs | 3 h 32 min1,270 subs |
| Heart NebulaEmission nebula, dual-band | 2 h 21 min845 subs | 3 h 10 min1,141 subs | 6 h 01 min2,166 subs |
| Rosette NebulaEmission nebula, dual-band | 1 h 12 min433 subs | 1 h 36 min574 subs | 2 h 57 min1,065 subs |
| Horsehead NebulaEmission nebula, dual-band | 1 h 40 min603 subs | 2 h 15 min808 subs | 4 h 13 min1,517 subs |
| Flame NebulaEmission nebula, dual-band | 28 min166 subs | 35 min213 subs | 1 h 02 min375 subs |
| California NebulaEmission nebula, dual-band | 1 h 40 min603 subs | 2 h 15 min808 subs | 4 h 13 min1,517 subs |
| Helix NebulaPlanetary nebula, dual-band | 1 h 40 min603 subs | 2 h 15 min808 subs | 4 h 13 min1,517 subs |
| Double ClusterOpen cluster | 5 min30 subs | 5 min30 subs | 6 min37 subs |
| NGC 891Galaxy | 1 h 26 min515 subs | 2 h 60 min1,079 subs | 8 h 24 min3,026 subs |
| Sombrero GalaxyGalaxy | 27 min162 subs | 51 min309 subs | 2 h 16 min817 subs |
| Sunflower GalaxyGalaxy | 53 min318 subs | 1 h 48 min649 subs | 4 h 59 min1,793 subs |
All 170 targets have a page for the Seestar S50 Pro.
Getting the most from the Seestar S50 Pro
20 s and longer subs need EQ mode; 60 s is the ceiling. Built-in filter wheel with dual-band filter.
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.
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.