How long to image the Rosette Nebula with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 1 h 36 min (574 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 24 min; a showpiece 6 h 23 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 08 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it only just fits, at 97% of the short side.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 16 min98 subs | 1 h 05 min390 subs | 4 h 20 min1,560 subs |
| Bortle 2Typical dark site | 16 min99 subs | 1 h 06 min396 subs | 4 h 24 min1,582 subs |
| Bortle 3Rural | 17 min102 subs | 1 h 08 min407 subs | 4 h 31 min1,625 subs |
| Bortle 4Rural / suburban transition | 18 min109 subs | 1 h 12 min433 subs | 4 h 48 min1,729 subs |
| Bortle 5Suburban | 20 min119 subs | 1 h 19 min474 subs | 5 h 15 min1,893 subs |
| Bortle 6Bright suburban | 24 min144 subs | 1 h 36 min574 subs | 6 h 23 min2,296 subs |
| Bortle 7Suburban / urban transition | 32 min192 subs | 2 h 08 min766 subs | 8 h 31 min3,064 subs |
| Bortle 8City | 44 min267 subs | 2 h 57 min1,065 subs | 12 h4,257 subs |
| Bortle 9Inner city | 1 h 11 min425 subs | 4 h 43 min1,700 subs | 19 h6,800 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 04 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, and 30% off the battery for a January night.)
- 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.
- 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 S50 Pro →
How it frames
The Rosette Nebula is 80′ × 60′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it only just fits, at 97% of the short side. Centre it carefully: there is no room to crop back afterwards.
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 | 1 h 08 min407 subs | 1 h 19 min474 subs | 2 h 08 min766 subs |
| 20 s | 49 min147 subs | 1 h180 subs | 1 h 49 min327 subs |
| 30 s | 43 min86 subs | 54 min108 subs | 1 h 43 min206 subs |
| 60 s | 36 min37 subs | 47 min48 subs | 1 h 36 min97 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 57 min341 subs | 1 h 33 min560 subs | 4 h 13 min1,517 subs |
| dual-band (LP filter) | 1 h 08 min407 subs | 1 h 19 min474 subs | 2 h 08 min766 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 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 Rosette Nebula 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
- Rosette Nebula with the ZWO Seestar S50: 1 h 25 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S30: 1 h 39 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 S50 Pro