How long to image the Rosette Nebula with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 1 h 39 min (597 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Rosette Nebula. A quick look takes 25 min; a showpiece 6 h 38 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 14 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is just over the frame at 1.1×.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 18 min107 subs | 1 h 11 min427 subs | 4 h 44 min1,707 subs |
| Bortle 2Typical dark site | 18 min108 subs | 1 h 12 min432 subs | 4 h 48 min1,728 subs |
| Bortle 3Rural | 18 min111 subs | 1 h 14 min442 subs | 4 h 54 min1,767 subs |
| Bortle 4Rural / suburban transition | 19 min117 subs | 1 h 18 min466 subs | 5 h 10 min1,863 subs |
| Bortle 5Suburban | 21 min126 subs | 1 h 24 min504 subs | 5 h 36 min2,015 subs |
| Bortle 6Bright suburban | 25 min150 subs | 1 h 39 min597 subs | 6 h 38 min2,388 subs |
| Bortle 7Suburban / urban transition | 32 min194 subs | 2 h 09 min775 subs | 8 h 36 min3,098 subs |
| Bortle 8City | 44 min263 subs | 2 h 55 min1,050 subs | 12 h4,200 subs |
| Bortle 9Inner city | 1 h 08 min410 subs | 4 h 33 min1,638 subs | 18 h6,552 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 09 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, and 30% off the battery for a January night.)
- 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.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the Seestar S30 →
How it frames
The Rosette Nebula is 80′ × 60′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it is just over the frame at 1.1×. Point at the part you want; the edges will fall outside the frame.
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 | 1 h 14 min442 subs | 1 h 24 min504 subs | 2 h 09 min775 subs |
| 20 s | 50 min152 subs | 1 h 01 min183 subs | 1 h 46 min318 subs |
| 30 s | 43 min86 subs | 53 min106 subs | 1 h 38 min197 subs |
| 60 s | 35 min35 subs | 45 min46 subs | 1 h 30 min91 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 58 min348 subs | 1 h 32 min551 subs | 3 h 59 min1,435 subs |
| dual-band (LP filter) | 1 h 14 min442 subs | 1 h 24 min504 subs | 2 h 09 min775 subs |
About the Rosette Nebula
A ring of hydrogen more than a degree across around the cluster NGC 2244. One of the best dual-band targets of winter and forgiving of light pollution.
NGC 2237, NGC 2244, Caldwell 49 · Emission nebula in Monoceros · magnitude 9.0 · 80′ × 60′ · best in Dec, Jan, Feb. 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 Rosette 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
- Rosette Nebula with the ZWO Seestar S50: 1 h 25 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S50 Pro: 1 h 36 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S30 Pro: 1 h 43 min from Bortle 6
- Rosette Nebula with the DwarfLab DWARF 3: 1 h 46 min from Bortle 6
- Rosette Nebula with the DwarfLab DWARF mini: 1 h 24 min from Bortle 6
- Rosette Nebula with the DwarfLab Draco: 1 h 08 min from Bortle 6
- Rosette Nebula with the DwarfLab DWARF II: 7 h 45 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera II: 2 h 15 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera Pro: 5 h 04 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera 3: 2 h 09 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera Pro 2: 4 h 49 min from Bortle 6
- Rosette Nebula with the Unistellar eQuinox 2: 2 h 04 min from Bortle 6
- Rosette Nebula with the Unistellar Odyssey: 9 h 33 min from Bortle 6
- Rosette Nebula with the Celestron Origin: 36 min from Bortle 6
- Rosette Nebula with the Celestron Origin Mark II: 49 min from Bortle 6
All telescopes for the Rosette Nebula · All targets for the Seestar S30