How long to image the Horsehead Nebula with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 2 h 15 min (808 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Horsehead Nebula. A quick look takes 34 min; a showpiece 8 h 58 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 34 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 72% 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 | 23 min136 subs | 1 h 30 min542 subs | 6 h 01 min2,166 subs |
| Bortle 2Typical dark site | 23 min138 subs | 1 h 32 min550 subs | 6 h 06 min2,199 subs |
| Bortle 3Rural | 24 min142 subs | 1 h 34 min566 subs | 6 h 17 min2,261 subs |
| Bortle 4Rural / suburban transition | 25 min151 subs | 1 h 40 min603 subs | 6 h 42 min2,411 subs |
| Bortle 5Suburban | 28 min166 subs | 1 h 50 min662 subs | 7 h 21 min2,648 subs |
| Bortle 6Bright suburban | 34 min202 subs | 2 h 15 min808 subs | 8 h 58 min3,231 subs |
| Bortle 7Suburban / urban transition | 45 min272 subs | 3 h 01 min1,086 subs | 12 h4,341 subs |
| Bortle 8City | 1 h 03 min380 subs | 4 h 13 min1,517 subs | 17 h6,065 subs |
| Bortle 9Inner city | 1 h 41 min609 subs | 6 h 46 min2,436 subs | 27 h9,741 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 55 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 December 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 Horsehead Nebula is 60′ × 10′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 72% of the frame’s short side.
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 34 min566 subs | 1 h 50 min662 subs | 3 h 01 min1,086 subs |
| 20 s | 1 h 07 min201 subs | 1 h 23 min250 subs | 2 h 34 min461 subs |
| 30 s | 58 min116 subs | 1 h 14 min148 subs | 2 h 25 min290 subs |
| 60 s | 49 min49 subs | 1 h 05 min65 subs | 2 h 15 min136 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 1 h 20 min478 subs | 2 h 12 min794 subs | 6 h 03 min2,177 subs |
| dual-band (LP filter) | 1 h 34 min566 subs | 1 h 50 min662 subs | 3 h 01 min1,086 subs |
About the Horsehead Nebula
The horse's head is a dark cloud in front of the glowing IC 434 ribbon. You image the ribbon; the head is what is missing. Dual-band, and expect a few hours from suburbia.
IC 434, Barnard 33 · Emission nebula in Orion · magnitude 7.3 · 60′ × 10′ · best in Nov, Dec, Jan. 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 Horsehead 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
- Horsehead Nebula with the ZWO Seestar S50: 2 h from Bortle 6
- Horsehead Nebula with the ZWO Seestar S30: 2 h 20 min from Bortle 6
- Horsehead Nebula with the ZWO Seestar S30 Pro: 2 h 25 min from Bortle 6
- Horsehead Nebula with the DwarfLab DWARF 3: 2 h 28 min from Bortle 6
- Horsehead Nebula with the DwarfLab DWARF mini: 1 h 58 min from Bortle 6
- Horsehead Nebula with the DwarfLab Draco: 1 h 35 min from Bortle 6
- Horsehead Nebula with the DwarfLab DWARF II: 11 h from Bortle 6
- Horsehead Nebula with the Vaonis Vespera II: 3 h 13 min from Bortle 6
- Horsehead Nebula with the Vaonis Vespera Pro: 7 h 14 min from Bortle 6
- Horsehead Nebula with the Vaonis Vespera 3: 3 h 05 min from Bortle 6
- Horsehead Nebula with the Vaonis Vespera Pro 2: 6 h 53 min from Bortle 6
- Horsehead Nebula with the Unistellar eQuinox 2: 2 h 57 min from Bortle 6
- Horsehead Nebula with the Unistellar Odyssey: 14 h from Bortle 6
- Horsehead Nebula with the Celestron Origin: 51 min from Bortle 6
- Horsehead Nebula with the Celestron Origin Mark II: 1 h 10 min from Bortle 6
All telescopes for the Horsehead Nebula · All targets for the Seestar S50 Pro