How long to image the Crescent Nebula with the Unistellar eQuinox 2
From a Bortle 6 suburban sky, the Unistellar eQuinox 2 needs about 4 h 14 min (3,814 subs of 4 s) for a solid image of the Crescent Nebula. A quick look takes 1 h 04 min; a showpiece 17 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 24 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 53% 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 | 33 min501 subs | 2 h 14 min2,003 subs | 8 h 54 min8,012 subs |
| Bortle 2Typical dark site | 34 min515 subs | 2 h 17 min2,059 subs | 9 h 09 min8,234 subs |
| Bortle 3Rural | 36 min541 subs | 2 h 24 min2,164 subs | 9 h 37 min8,655 subs |
| Bortle 4Rural / suburban transition | 40 min605 subs | 2 h 41 min2,419 subs | 11 h9,674 subs |
| Bortle 5Suburban | 47 min706 subs | 3 h 08 min2,823 subs | 13 h11,290 subs |
| Bortle 6Bright suburban | 1 h 04 min954 subs | 4 h 14 min3,814 subs | 17 h15,253 subs |
| Bortle 7Suburban / urban transition | 1 h 35 min1,426 subs | 6 h 20 min5,702 subs | 25 h22,805 subs |
| Bortle 8City | 2 h 24 min2,159 subs | 9 h 36 min8,633 subs | 38 h34,531 subs |
| Bortle 9Inner city | 4 h 08 min3,722 subs | 17 h14,885 subs | 66 h59,540 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 5 h 30 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.)
- 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.
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Everything that fits the eQuinox 2 →
How it frames
The Crescent Nebula is 18′ × 12′ across. The eQuinox 2 frames 0.76° × 0.57° at 1.33″ per pixel, so it fills 53% of the frame’s short side.
Filters
The Crescent 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 Crescent Nebula
A shell blown by a Wolf-Rayet star, bright in H-alpha with a faint OIII skin. Small, so the bigger scopes do it justice.
NGC 6888, Caldwell 27 · Emission nebula in Cygnus · magnitude 7.4 · 18′ × 12′ · best in Jul, Aug, Sep. 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 Crescent 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
- Crescent Nebula with the ZWO Seestar S50: 2 h 49 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S50 Pro: 3 h 10 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S30: 3 h 19 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S30 Pro: 3 h 25 min from Bortle 6
- Crescent Nebula with the DwarfLab DWARF 3: 3 h 27 min from Bortle 6
- Crescent Nebula with the DwarfLab DWARF mini: 2 h 47 min from Bortle 6
- Crescent Nebula with the DwarfLab Draco: 2 h 14 min from Bortle 6
- Crescent Nebula with the DwarfLab DWARF II: 16 h from Bortle 6
- Crescent Nebula with the Vaonis Vespera II: 4 h 37 min from Bortle 6
- Crescent Nebula with the Vaonis Vespera Pro: 10 h from Bortle 6
- Crescent Nebula with the Vaonis Vespera 3: 4 h 24 min from Bortle 6
- Crescent Nebula with the Vaonis Vespera Pro 2: 9 h 52 min from Bortle 6
- Crescent Nebula with the Unistellar Odyssey: 20 h from Bortle 6
- Crescent Nebula with the Celestron Origin: 1 h 13 min from Bortle 6
- Crescent Nebula with the Celestron Origin Mark II: 1 h 40 min from Bortle 6
All telescopes for the Crescent Nebula · All targets for the eQuinox 2