How long to image the Horsehead Nebula with the Unistellar eQuinox 2
From a Bortle 6 suburban sky, the Unistellar eQuinox 2 needs about 2 h 57 min (2,657 subs of 4 s) for a solid image of the Horsehead Nebula. A quick look takes 44 min; a showpiece 12 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 41 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is 1.8× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 23 min352 subs | 1 h 34 min1,405 subs | 6 h 14 min5,617 subs |
| Bortle 2Typical dark site | 24 min361 subs | 1 h 36 min1,443 subs | 6 h 25 min5,771 subs |
| Bortle 3Rural | 25 min379 subs | 1 h 41 min1,516 subs | 6 h 44 min6,062 subs |
| Bortle 4Rural / suburban transition | 28 min423 subs | 1 h 53 min1,692 subs | 7 h 31 min6,767 subs |
| Bortle 5Suburban | 33 min493 subs | 2 h 11 min1,971 subs | 8 h 46 min7,884 subs |
| Bortle 6Bright suburban | 44 min665 subs | 2 h 57 min2,657 subs | 12 h10,626 subs |
| Bortle 7Suburban / urban transition | 1 h 06 min991 subs | 4 h 24 min3,963 subs | 18 h15,851 subs |
| Bortle 8City | 1 h 40 min1,498 subs | 6 h 39 min5,991 subs | 27 h23,964 subs |
| Bortle 9Inner city | 2 h 52 min2,580 subs | 11 h10,317 subs | 46 h41,265 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 50 min of run time. The eQuinox 2’s battery (rated about 11 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 power bank 20000mAh 5V 2AUnistellar asks for a 5 V 2 A output; PD is not needed.
- 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 eQuinox 2 →
How it frames
The Horsehead Nebula is 60′ × 10′ across. The eQuinox 2 frames 0.76° × 0.57° at 1.33″ per pixel, so it is 1.8× wider than the frame. A mosaic, or choosing the part you want and letting the rest go, is how it gets shot on this scope.
Filters
The Horsehead Nebula is an emission target, where a dual-band filter would normally cut the time several-fold from a lit sky, but the eQuinox 2 has no dual-band option: No built-in filter. Unistellar sells only a solar filter and says a third-party filter is at your own risk and voids the warranty. The figures above are for the No filter position, and a darker sky is the lever that remains.
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 Unistellar eQuinox 2
A 114 mm Newtonian with five times the light grasp of a 50 mm refractor. Fixed 4 s subs put it in read-noise territory under dark skies, but the aperture carries it. The published field is 45.6′ × 34.2′, a crop of the sensor.
Fixed 4 s subs in Enhanced Vision; they cannot be changed. No built-in filter. Unistellar sells only a solar filter and says a third-party filter is at your own risk and voids the warranty.
The eQuinox 2 uses fixed 4 s subs, so the only levers you have are the sky you shoot from, the filter, and total time.
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 eQuinox 2? 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 S50 Pro: 2 h 15 min 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 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 eQuinox 2