How long to image the Ring Nebula with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 7 min (45 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Ring Nebula. A quick look takes 2 min; a showpiece 30 min. Under a Bortle 3 rural sky the solid figure drops to 6 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 21 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 2 min10 subs | 6 min39 subs | 25 min153 subs |
| Bortle 2Typical dark site | 2 min10 subs | 6 min39 subs | 26 min154 subs |
| Bortle 3Rural | 2 min10 subs | 6 min39 subs | 26 min156 subs |
| Bortle 4Rural / suburban transition | 2 min10 subs | 7 min40 subs | 26 min159 subs |
| Bortle 5Suburban | 2 min11 subs | 7 min42 subs | 27 min165 subs |
| Bortle 6Bright suburban | 2 min12 subs | 7 min45 subs | 30 min180 subs |
| Bortle 7Suburban / urban transition | 2 min13 subs | 9 min52 subs | 35 min208 subs |
| Bortle 8City | 3 min16 subs | 10 min63 subs | 42 min251 subs |
| Bortle 9Inner city | 4 min22 subs | 14 min86 subs | 57 min343 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 10 min of run time. The Seestar S30’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 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
- Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and 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 S30 →
How it frames
The Ring Nebula is 1.4′ × 1′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it is small in the frame, about 21 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, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 6 min39 subs | 7 min42 subs | 9 min52 subs |
| 20 s | 10 min30 subs | 10 min30 subs | 10 min30 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) | 5 min30 subs | 6 min37 subs | 12 min72 subs |
| dual-band (LP filter) | 6 min39 subs | 7 min42 subs | 9 min52 subs |
About the Ring Nebula
A tiny, bright smoke ring. It is small in a smart scope but so bright per pixel that a few minutes show the ring; the faint outer halo is another matter.
M57, NGC 6720 · Planetary nebula in Lyra · magnitude 8.8 · 1.4′ × 1′ · 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 S30
Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters.
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 Ring Nebula from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Ring Nebula with the ZWO Seestar S50: 7 min from Bortle 6
- Ring Nebula with the ZWO Seestar S50 Pro: 8 min from Bortle 6
- Ring Nebula with the ZWO Seestar S30 Pro: 8 min from Bortle 6
- Ring Nebula with the DwarfLab DWARF 3: 10 min from Bortle 6
- Ring Nebula with the DwarfLab DWARF mini: 8 min from Bortle 6
- Ring Nebula with the DwarfLab Draco: 15 min from Bortle 6
- Ring Nebula with the DwarfLab DWARF II: 25 min from Bortle 6
- Ring Nebula with the Vaonis Vespera II: 8 min from Bortle 6
- Ring Nebula with the Vaonis Vespera Pro: 17 min from Bortle 6
- Ring Nebula with the Vaonis Vespera 3: 7 min from Bortle 6
- Ring Nebula with the Vaonis Vespera Pro 2: 16 min from Bortle 6
- Ring Nebula with the Unistellar eQuinox 2: 6 min from Bortle 6
- Ring Nebula with the Unistellar Odyssey: 28 min from Bortle 6
- Ring Nebula with the Celestron Origin: 5 min from Bortle 6
- Ring Nebula with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the Ring Nebula · All targets for the Seestar S30