How long to image the NGC 6781 with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 3 h 02 min (1,091 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 45 min; a showpiece 12 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 09 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 47 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 31 min187 subs | 2 h 04 min746 subs | 8 h 17 min2,984 subs |
| Bortle 2Typical dark site | 32 min190 subs | 2 h 06 min757 subs | 8 h 24 min3,026 subs |
| Bortle 3Rural | 32 min195 subs | 2 h 09 min777 subs | 8 h 38 min3,106 subs |
| Bortle 4Rural / suburban transition | 34 min207 subs | 2 h 17 min825 subs | 9 h 10 min3,300 subs |
| Bortle 5Suburban | 38 min226 subs | 2 h 30 min902 subs | 10 h3,608 subs |
| Bortle 6Bright suburban | 45 min273 subs | 3 h 02 min1,091 subs | 12 h4,362 subs |
| Bortle 7Suburban / urban transition | 1 h363 subs | 4 h 02 min1,450 subs | 16 h5,799 subs |
| Bortle 8City | 1 h 24 min502 subs | 5 h 35 min2,008 subs | 22 h8,031 subs |
| Bortle 9Inner city | 2 h 13 min800 subs | 8 h 53 min3,198 subs | 36 h12,791 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 56 min of run time. The Seestar S50 Pro’s battery (rated about 9 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 PD power bank 20000mAh 30WAccepts 12 V 3 A PD, so a 30 W bank tops up the 10,000 mAh cell while imaging.
- Seestar S50 Pro dew shieldDew heater is built in; a shield adds margin on damp nights. Check the listing says S50 Pro.
- 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 Pro →
How it frames
The NGC 6781 is 1.8′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it is small in the frame, about 47 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, and 60 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 2 h 09 min777 subs | 2 h 30 min902 subs | 4 h 02 min1,450 subs |
| 20 s | 1 h 34 min283 subs | 1 h 55 min345 subs | 3 h 26 min619 subs |
| 30 s | 1 h 22 min165 subs | 1 h 43 min207 subs | 3 h 15 min390 subs |
| 60 s | 1 h 11 min71 subs | 1 h 31 min92 subs | 3 h 03 min183 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 1 h 48 min650 subs | 2 h 57 min1,060 subs | 7 h 55 min2,850 subs |
| dual-band (LP filter) | 2 h 09 min777 subs | 2 h 30 min902 subs | 4 h 02 min1,450 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 Pro
The S50 optics at 260 mm on an 8 MP 1/1.2-inch sensor: a wider, taller field, four times the pixels, and 60 s subs in EQ mode. Per pixel it is a whisker slower than the S50 because of the longer focal length; the long subs make it the better dark-site scope.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters on the telephoto camera.
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 Pro? 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: 2 h 42 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 Pro