How long to image the NGC 6781 with the Unistellar eQuinox 2
From a Bortle 6 suburban sky, the Unistellar eQuinox 2 needs about 3 h 52 min (3,485 subs of 4 s) for a solid image of the NGC 6781. A quick look takes 58 min; a showpiece 15 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 14 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 5% 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 | 31 min466 subs | 2 h 04 min1,863 subs | 8 h 17 min7,452 subs |
| Bortle 2Typical dark site | 32 min479 subs | 2 h 08 min1,913 subs | 8 h 30 min7,652 subs |
| Bortle 3Rural | 33 min502 subs | 2 h 14 min2,007 subs | 8 h 55 min8,028 subs |
| Bortle 4Rural / suburban transition | 37 min559 subs | 2 h 29 min2,236 subs | 9 h 56 min8,941 subs |
| Bortle 5Suburban | 43 min650 subs | 2 h 53 min2,597 subs | 12 h10,388 subs |
| Bortle 6Bright suburban | 58 min872 subs | 3 h 52 min3,485 subs | 15 h13,939 subs |
| Bortle 7Suburban / urban transition | 1 h 26 min1,294 subs | 5 h 45 min5,176 subs | 23 h20,704 subs |
| Bortle 8City | 2 h 10 min1,951 subs | 8 h 40 min7,802 subs | 35 h31,207 subs |
| Bortle 9Inner city | 3 h 43 min3,351 subs | 15 h13,402 subs | 60 h53,608 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 5 h 02 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 NGC 6781 is 1.8′ across. The eQuinox 2 frames 0.76° × 0.57° at 1.33″ per pixel, so it fills 5% of the frame’s short side.
Filters
The NGC 6781 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 NGC 6781
A ghostly ring planetary in Aquila, larger and fainter than the Ring Nebula. Dual-band recommended.
Aquila planetary · Planetary nebula in Aquila · magnitude 11.4 · 1.8′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
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 NGC 6781 from a eQuinox 2? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 6781 with the ZWO Seestar S50: 2 h 42 min from Bortle 6
- NGC 6781 with the ZWO Seestar S50 Pro: 3 h 02 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30: 3 h 09 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30 Pro: 3 h 16 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF 3: 3 h 22 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF mini: 2 h 40 min from Bortle 6
- NGC 6781 with the DwarfLab Draco: 2 h 08 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF II: 15 h from Bortle 6
- NGC 6781 with the Vaonis Vespera II: 4 h 15 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro: 9 h 32 min from Bortle 6
- NGC 6781 with the Vaonis Vespera 3: 4 h 04 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro 2: 9 h 05 min from Bortle 6
- NGC 6781 with the Unistellar Odyssey: 18 h from Bortle 6
- NGC 6781 with the Celestron Origin: 1 h 07 min from Bortle 6
- NGC 6781 with the Celestron Origin Mark II: 1 h 33 min from Bortle 6
All telescopes for the NGC 6781 · All targets for the eQuinox 2