How long to image the NGC 6781 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 18 h (16,142 subs of 4 s) for a solid image of the NGC 6781. A quick look takes 4 h 29 min; a showpiece 72 h. Under a Bortle 3 rural sky the solid figure drops to 12 h. 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 | 2 h 51 min2,561 subs | 11 h10,242 subs | 46 h40,968 subs |
| Bortle 2Typical dark site | 2 h 54 min2,606 subs | 12 h10,424 subs | 46 h41,693 subs |
| Bortle 3Rural | 2 h 59 min2,692 subs | 12 h10,766 subs | 48 h43,064 subs |
| Bortle 4Rural / suburban transition | 3 h 13 min2,900 subs | 13 h11,597 subs | 52 h46,386 subs |
| Bortle 5Suburban | 3 h 35 min3,229 subs | 14 h12,913 subs | 57 h51,650 subs |
| Bortle 6Bright suburban | 4 h 29 min4,036 subs | 18 h16,142 subs | 72 h64,568 subs |
| Bortle 7Suburban / urban transition | 6 h 12 min5,574 subs | 25 h22,296 subs | 99 h89,181 subs |
| Bortle 8City | 8 h 51 min7,963 subs | 35 h31,849 subs | 140+ h127,396 subs |
| Bortle 9Inner city | 15 h13,057 subs | 58 h52,225 subs | 230+ h208,899 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 23 h of run time. That is more than one night: over 4 nights, about 5 h 50 min each. The Odyssey’s battery is rated at about 5 h, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB power bank 20000mAh 5V 2.4AUnistellar says plain 5 V 2.4 A and warns against fast or adaptive chargers.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames
The NGC 6781 is 1.8′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ 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 Odyssey has no dual-band option: No filter option; Unistellar says third-party filters cannot be fitted to the Odyssey. 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 Odyssey
Unistellar’s compact 85 mm with autofocus and tiny pixels. Sharp, but the fine sampling costs time on faint extended targets. The Odyssey Pro is the same telescope with an eyepiece added, so these figures apply to both.
Fixed 4 s subs in Enhanced Vision; they cannot be changed. No filter option; Unistellar says third-party filters cannot be fitted to the Odyssey.
The Odyssey 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 Odyssey? 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 eQuinox 2: 3 h 52 min 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 Odyssey