How long to image the Rosette Nebula with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 1 h 43 min (619 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 26 min; a showpiece 6 h 52 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 fills 59% 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 | 18 min107 subs | 1 h 11 min425 subs | 4 h 43 min1,700 subs |
| Bortle 2Typical dark site | 18 min108 subs | 1 h 12 min431 subs | 4 h 47 min1,724 subs |
| Bortle 3Rural | 18 min111 subs | 1 h 14 min443 subs | 4 h 55 min1,769 subs |
| Bortle 4Rural / suburban transition | 20 min118 subs | 1 h 18 min470 subs | 5 h 13 min1,878 subs |
| Bortle 5Suburban | 21 min129 subs | 1 h 25 min513 subs | 5 h 42 min2,051 subs |
| Bortle 6Bright suburban | 26 min155 subs | 1 h 43 min619 subs | 6 h 52 min2,475 subs |
| Bortle 7Suburban / urban transition | 34 min206 subs | 2 h 17 min821 subs | 9 h 07 min3,283 subs |
| Bortle 8City | 47 min284 subs | 3 h 09 min1,135 subs | 13 h4,537 subs |
| Bortle 9Inner city | 1 h 15 min451 subs | 5 h 01 min1,804 subs | 20 h7,213 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 14 min of run time. The Seestar S30 Pro’s battery (rated about 5 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 3A5 V 3 A input and it runs while charging.
- Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
- 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 Pro →
How it frames
The Rosette Nebula is 80′ × 60′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 59% 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 | 1 h 14 min443 subs | 1 h 25 min513 subs | 2 h 17 min821 subs |
| 20 s | 53 min159 subs | 1 h 05 min194 subs | 1 h 56 min348 subs |
| 30 s | 46 min92 subs | 58 min116 subs | 1 h 49 min218 subs |
| 60 s | 39 min39 subs | 51 min51 subs | 1 h 42 min102 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 1 h 01 min366 subs | 1 h 39 min597 subs | 4 h 27 min1,603 subs |
| dual-band (LP filter) | 1 h 14 min443 subs | 1 h 25 min513 subs | 2 h 17 min821 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 Pro
The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.
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 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 Rosette Nebula from a Seestar S30 Pro? 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: 1 h 39 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 Pro