How long to image the Saturn Nebula with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 10 min (62 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Saturn Nebula. A quick look takes 3 min; a showpiece 41 min. Under a Bortle 3 rural sky the solid figure drops to 9 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is small in the frame, about 18 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 2 min13 subs | 8 min51 subs | 33 min201 subs |
| Bortle 2Typical dark site | 2 min13 subs | 8 min51 subs | 34 min203 subs |
| Bortle 3Rural | 2 min13 subs | 9 min52 subs | 34 min205 subs |
| Bortle 4Rural / suburban transition | 2 min14 subs | 9 min53 subs | 35 min212 subs |
| Bortle 5Suburban | 2 min14 subs | 9 min56 subs | 37 min222 subs |
| Bortle 6Bright suburban | 3 min16 subs | 10 min62 subs | 41 min247 subs |
| Bortle 7Suburban / urban transition | 3 min19 subs | 12 min74 subs | 49 min296 subs |
| Bortle 8City | 4 min24 subs | 15 min93 subs | 1 h 02 min371 subs |
| Bortle 9Inner city | 6 min34 subs | 22 min133 subs | 1 h 28 min530 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 13 min of run time. The Seestar S50’s battery (rated about 6 h) should cover it; a power bank still keeps the phone running the app alive. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
- Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks stray light.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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Everything that fits the Seestar S50 →
How it frames
The Saturn Nebula is 0.7′ × 0.4′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is small in the frame, about 18 pixels across. It is worth doing, but the result is a crop rather than a full frame; a longer focal length would resolve more of it.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 9 min52 subs | 9 min56 subs | 12 min74 subs |
| 20 s | 10 min30 subs | 10 min30 subs | 11 min34 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 15 min30 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 7 min40 subs | 9 min54 subs | 19 min114 subs |
| dual-band (LP filter) | 9 min52 subs | 9 min56 subs | 12 min74 subs |
About the Saturn Nebula
A bright planetary with ansae like Saturn's rings, tiny in a smart scope but very bright per pixel.
NGC 7009, Caldwell 55 · Planetary nebula in Aquarius · magnitude 8.0 · 0.7′ × 0.4′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
About the ZWO Seestar S50
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.
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.
Have an image of the Saturn Nebula from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Saturn Nebula with the ZWO Seestar S50 Pro: 11 min from Bortle 6
- Saturn Nebula with the ZWO Seestar S30: 11 min from Bortle 6
- Saturn Nebula with the ZWO Seestar S30 Pro: 12 min from Bortle 6
- Saturn Nebula with the DwarfLab DWARF 3: 14 min from Bortle 6
- Saturn Nebula with the DwarfLab DWARF mini: 10 min from Bortle 6
- Saturn Nebula with the DwarfLab Draco: 15 min from Bortle 6
- Saturn Nebula with the DwarfLab DWARF II: 40 min from Bortle 6
- Saturn Nebula with the Vaonis Vespera II: 12 min from Bortle 6
- Saturn Nebula with the Vaonis Vespera Pro: 27 min from Bortle 6
- Saturn Nebula with the Vaonis Vespera 3: 12 min from Bortle 6
- Saturn Nebula with the Vaonis Vespera Pro 2: 26 min from Bortle 6
- Saturn Nebula with the Unistellar eQuinox 2: 10 min from Bortle 6
- Saturn Nebula with the Unistellar Odyssey: 46 min from Bortle 6
- Saturn Nebula with the Celestron Origin: 5 min from Bortle 6
- Saturn Nebula with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the Saturn Nebula · All targets for the Seestar S50