How long to image the Bow-Tie Nebula with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 21 min (125 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Bow-Tie Nebula. A quick look takes 5 min; a showpiece 1 h 23 min. Under a Bortle 3 rural sky the solid figure drops to 16 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 20 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 4 min24 subs | 16 min96 subs | 1 h 04 min383 subs |
| Bortle 2Typical dark site | 4 min25 subs | 16 min97 subs | 1 h 04 min387 subs |
| Bortle 3Rural | 4 min25 subs | 16 min99 subs | 1 h 06 min394 subs |
| Bortle 4Rural / suburban transition | 4 min26 subs | 17 min103 subs | 1 h 08 min410 subs |
| Bortle 5Suburban | 5 min28 subs | 18 min109 subs | 1 h 13 min436 subs |
| Bortle 6Bright suburban | 5 min32 subs | 21 min125 subs | 1 h 23 min500 subs |
| Bortle 7Suburban / urban transition | 6 min39 subs | 26 min156 subs | 1 h 43 min621 subs |
| Bortle 8City | 8 min51 subs | 34 min203 subs | 2 h 15 min809 subs |
| Bortle 9Inner city | 13 min76 subs | 50 min303 subs | 3 h 22 min1,210 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 27 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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How it frames
The Bow-Tie Nebula is 0.8′ × 0.6′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is small in the frame, about 20 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 | 16 min99 subs | 18 min109 subs | 26 min156 subs |
| 20 s | 14 min41 subs | 15 min47 subs | 23 min70 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 22 min45 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) | 13 min79 subs | 19 min113 subs | 44 min264 subs |
| dual-band (LP filter) | 16 min99 subs | 18 min109 subs | 26 min156 subs |
About the Bow-Tie Nebula
A red-tinged planetary near the pole with a bright central star. Small; dual-band brings out the bow.
NGC 40, Caldwell 2 · Planetary nebula in Cepheus · magnitude 11.6 · 0.8′ × 0.6′ · best in Sep, Oct, Nov. 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 Bow-Tie 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
- Bow-Tie Nebula with the ZWO Seestar S50 Pro: 23 min from Bortle 6
- Bow-Tie Nebula with the ZWO Seestar S30: 23 min from Bortle 6
- Bow-Tie Nebula with the ZWO Seestar S30 Pro: 25 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF 3: 28 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF mini: 21 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab Draco: 17 min from Bortle 6
- Bow-Tie Nebula with the DwarfLab DWARF II: 1 h 32 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera II: 27 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera Pro: 1 h 01 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera 3: 26 min from Bortle 6
- Bow-Tie Nebula with the Vaonis Vespera Pro 2: 58 min from Bortle 6
- Bow-Tie Nebula with the Unistellar eQuinox 2: 24 min from Bortle 6
- Bow-Tie Nebula with the Unistellar Odyssey: 1 h 48 min from Bortle 6
- Bow-Tie Nebula with the Celestron Origin: 7 min from Bortle 6
- Bow-Tie Nebula with the Celestron Origin Mark II: 10 min from Bortle 6
All telescopes for the Bow-Tie Nebula · All targets for the Seestar S50