How long to image the NGC 6781 with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 2 h 42 min (973 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the NGC 6781. A quick look takes 41 min; a showpiece 11 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 54 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 45 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 27 min164 subs | 1 h 49 min655 subs | 7 h 16 min2,617 subs |
| Bortle 2Typical dark site | 28 min166 subs | 1 h 51 min664 subs | 7 h 23 min2,656 subs |
| Bortle 3Rural | 28 min171 subs | 1 h 54 min683 subs | 7 h 35 min2,730 subs |
| Bortle 4Rural / suburban transition | 30 min182 subs | 2 h 01 min728 subs | 8 h 05 min2,909 subs |
| Bortle 5Suburban | 33 min200 subs | 2 h 13 min799 subs | 8 h 52 min3,194 subs |
| Bortle 6Bright suburban | 41 min244 subs | 2 h 42 min973 subs | 11 h3,891 subs |
| Bortle 7Suburban / urban transition | 54 min327 subs | 3 h 37 min1,305 subs | 14 h5,220 subs |
| Bortle 8City | 1 h 16 min456 subs | 5 h 03 min1,821 subs | 20 h7,284 subs |
| Bortle 9Inner city | 2 h 02 min731 subs | 8 h 07 min2,922 subs | 32 h11,685 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 31 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.
Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.
Everything that fits the Seestar S50 →
How it frames
The NGC 6781 is 1.8′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is small in the frame, about 45 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 | 1 h 54 min683 subs | 2 h 13 min799 subs | 3 h 37 min1,305 subs |
| 20 s | 1 h 24 min251 subs | 1 h 43 min309 subs | 3 h 07 min562 subs |
| 30 s | 1 h 14 min148 subs | 1 h 33 min186 subs | 2 h 57 min355 subs |
| 60 s | 1 h 03 min64 subs | 1 h 23 min83 subs | 2 h 47 min168 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 1 h 37 min584 subs | 2 h 40 min962 subs | 7 h 16 min2,617 subs |
| dual-band (LP filter) | 1 h 54 min683 subs | 2 h 13 min799 subs | 3 h 37 min1,305 subs |
About the NGC 6781
A ghostly ring planetary in Aquila, larger and fainter than the Ring Nebula. Dual-band recommended.
Aquila planetary · Planetary nebula in Aquila · magnitude 11.4 · 1.8′ · best in Jun, Jul, Aug. 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 NGC 6781 from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 6781 with the ZWO Seestar S50 Pro: 3 h 02 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30: 3 h 09 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30 Pro: 3 h 16 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF 3: 3 h 22 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF mini: 2 h 40 min from Bortle 6
- NGC 6781 with the DwarfLab Draco: 2 h 08 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF II: 15 h from Bortle 6
- NGC 6781 with the Vaonis Vespera II: 4 h 15 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro: 9 h 32 min from Bortle 6
- NGC 6781 with the Vaonis Vespera 3: 4 h 04 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro 2: 9 h 05 min from Bortle 6
- NGC 6781 with the Unistellar eQuinox 2: 3 h 52 min from Bortle 6
- NGC 6781 with the Unistellar Odyssey: 18 h from Bortle 6
- NGC 6781 with the Celestron Origin: 1 h 07 min from Bortle 6
- NGC 6781 with the Celestron Origin Mark II: 1 h 33 min from Bortle 6
All telescopes for the NGC 6781 · All targets for the Seestar S50