How long to image the Trifid Nebula with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 44 min (263 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Trifid Nebula. A quick look takes 11 min; a showpiece 2 h 55 min. Under a Bortle 3 rural sky the solid figure drops to 31 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 65% of the frame’s short side.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 8 min46 subs | 30 min182 subs | 2 h 01 min725 subs |
| Bortle 2Typical dark site | 8 min46 subs | 31 min184 subs | 2 h 02 min735 subs |
| Bortle 3Rural | 8 min48 subs | 31 min189 subs | 2 h 06 min754 subs |
| Bortle 4Rural / suburban transition | 8 min50 subs | 33 min200 subs | 2 h 13 min800 subs |
| Bortle 5Suburban | 9 min55 subs | 36 min219 subs | 2 h 25 min873 subs |
| Bortle 6Bright suburban | 11 min66 subs | 44 min263 subs | 2 h 55 min1,051 subs |
| Bortle 7Suburban / urban transition | 14 min87 subs | 58 min348 subs | 3 h 52 min1,391 subs |
| Bortle 8City | 20 min120 subs | 1 h 20 min480 subs | 5 h 20 min1,919 subs |
| Bortle 9Inner city | 32 min191 subs | 2 h 07 min761 subs | 8 h 27 min3,044 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 57 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 Trifid Nebula is 28′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 65% of the frame’s short side.
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 | 31 min189 subs | 36 min219 subs | 58 min348 subs |
| 20 s | 24 min72 subs | 29 min86 subs | 50 min151 subs |
| 30 s | 21 min43 subs | 26 min53 subs | 48 min96 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 45 min46 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 26 min159 subs | 43 min256 subs | 1 h 53 min680 subs |
| dual-band (LP filter) | 31 min189 subs | 36 min219 subs | 58 min348 subs |
About the Trifid Nebula
Red emission, blue reflection and dark lanes in one object. Shoot it without a filter to keep the blue, or dual-band for the red.
M20, NGC 6514 · Emission nebula in Sagittarius · magnitude 6.3 · 28′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.
Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.
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 Trifid 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
- Trifid Nebula with the ZWO Seestar S50 Pro: 49 min from Bortle 6
- Trifid Nebula with the ZWO Seestar S30: 51 min from Bortle 6
- Trifid Nebula with the ZWO Seestar S30 Pro: 53 min from Bortle 6
- Trifid Nebula with the DwarfLab DWARF 3: 55 min from Bortle 6
- Trifid Nebula with the DwarfLab DWARF mini: 43 min from Bortle 6
- Trifid Nebula with the DwarfLab Draco: 35 min from Bortle 6
- Trifid Nebula with the DwarfLab DWARF II: 3 h 48 min from Bortle 6
- Trifid Nebula with the Vaonis Vespera II: 1 h 07 min from Bortle 6
- Trifid Nebula with the Vaonis Vespera Pro: 2 h 30 min from Bortle 6
- Trifid Nebula with the Vaonis Vespera 3: 1 h 04 min from Bortle 6
- Trifid Nebula with the Vaonis Vespera Pro 2: 2 h 23 min from Bortle 6
- Trifid Nebula with the Unistellar eQuinox 2: 1 h from Bortle 6
- Trifid Nebula with the Unistellar Odyssey: 4 h 39 min from Bortle 6
- Trifid Nebula with the Celestron Origin: 18 min from Bortle 6
- Trifid Nebula with the Celestron Origin Mark II: 24 min from Bortle 6
All telescopes for the Trifid Nebula · All targets for the Seestar S50