How long to image the Cocoon Nebula with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 3 h 29 min (1,253 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Cocoon Nebula. A quick look takes 52 min; a showpiece 14 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 33 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 17% 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 | 37 min221 subs | 2 h 27 min883 subs | 9 h 49 min3,532 subs |
| Bortle 2Typical dark site | 37 min224 subs | 2 h 29 min895 subs | 9 h 56 min3,577 subs |
| Bortle 3Rural | 38 min229 subs | 2 h 33 min916 subs | 10 h3,663 subs |
| Bortle 4Rural / suburban transition | 40 min242 subs | 2 h 41 min968 subs | 11 h3,871 subs |
| Bortle 5Suburban | 44 min263 subs | 2 h 55 min1,051 subs | 12 h4,201 subs |
| Bortle 6Bright suburban | 52 min314 subs | 3 h 29 min1,253 subs | 14 h5,011 subs |
| Bortle 7Suburban / urban transition | 1 h 08 min410 subs | 4 h 33 min1,639 subs | 18 h6,554 subs |
| Bortle 8City | 1 h 33 min560 subs | 6 h 13 min2,238 subs | 25 h8,949 subs |
| Bortle 9Inner city | 2 h 26 min879 subs | 9 h 46 min3,515 subs | 39 h14,057 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 4 h 31 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 Cocoon Nebula is 12′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 17% of the frame’s short side.
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 | 2 h 33 min916 subs | 2 h 55 min1,051 subs | 4 h 33 min1,639 subs |
| 20 s | 1 h 42 min307 subs | 2 h 05 min374 subs | 3 h 43 min668 subs |
| 30 s | 1 h 25 min171 subs | 1 h 48 min216 subs | 3 h 26 min412 subs |
| 60 s | 1 h 09 min69 subs | 1 h 31 min91 subs | 3 h 09 min190 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 2 h 01 min725 subs | 3 h 14 min1,165 subs | 8 h 34 min3,086 subs |
| dual-band (LP filter) | 2 h 33 min916 subs | 2 h 55 min1,051 subs | 4 h 33 min1,639 subs |
About the Cocoon Nebula
A round emission and reflection nebula at the end of a long dark lane. Mixed light, so a broadband stack keeps the blue.
IC 5146, Caldwell 19 · Emission nebula in Cygnus · magnitude 7.2 · 12′ · best in Jul, Aug, Sep. 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 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 Cocoon 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
- Cocoon Nebula with the ZWO Seestar S50: 2 h 58 min from Bortle 6
- Cocoon Nebula with the ZWO Seestar S50 Pro: 3 h 20 min from Bortle 6
- Cocoon Nebula with the ZWO Seestar S30 Pro: 3 h 36 min from Bortle 6
- Cocoon Nebula with the DwarfLab DWARF 3: 3 h 39 min from Bortle 6
- Cocoon Nebula with the DwarfLab DWARF mini: 2 h 55 min from Bortle 6
- Cocoon Nebula with the DwarfLab Draco: 2 h 21 min from Bortle 6
- Cocoon Nebula with the DwarfLab DWARF II: 17 h from Bortle 6
- Cocoon Nebula with the Vaonis Vespera II: 4 h 49 min from Bortle 6
- Cocoon Nebula with the Vaonis Vespera Pro: 11 h from Bortle 6
- Cocoon Nebula with the Vaonis Vespera 3: 4 h 36 min from Bortle 6
- Cocoon Nebula with the Vaonis Vespera Pro 2: 10 h from Bortle 6
- Cocoon Nebula with the Unistellar eQuinox 2: 4 h 25 min from Bortle 6
- Cocoon Nebula with the Unistellar Odyssey: 21 h from Bortle 6
- Cocoon Nebula with the Celestron Origin: 1 h 16 min from Bortle 6
- Cocoon Nebula with the Celestron Origin Mark II: 1 h 44 min from Bortle 6
All telescopes for the Cocoon Nebula · All targets for the Seestar S30