How long to image the NGC 6939 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 19 min (291 subs of 4 s) for a solid image of the NGC 6939. A quick look takes 5 min; a showpiece 1 h 18 min. Under a Bortle 3 rural sky the solid figure drops to 14 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 21% 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 | 3 min53 subs | 14 min210 subs | 56 min838 subs |
| Bortle 2Typical dark site | 4 min53 subs | 14 min212 subs | 57 min848 subs |
| Bortle 3Rural | 4 min55 subs | 14 min217 subs | 58 min867 subs |
| Bortle 4Rural / suburban transition | 4 min58 subs | 15 min229 subs | 1 h 01 min913 subs |
| Bortle 5Suburban | 4 min62 subs | 16 min247 subs | 1 h 06 min985 subs |
| Bortle 6Bright suburban | 5 min73 subs | 19 min291 subs | 1 h 18 min1,163 subs |
| Bortle 7Suburban / urban transition | 6 min94 subs | 25 min376 subs | 1 h 40 min1,502 subs |
| Bortle 8City | 8 min127 subs | 34 min507 subs | 2 h 15 min2,028 subs |
| Bortle 9Inner city | 13 min197 subs | 52 min788 subs | 3 h 30 min3,150 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 25 min of run time. The Odyssey’s battery (rated about 5 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 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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Everything that fits the Odyssey →
How it frames
The NGC 6939 is 7′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 21% of the frame’s short side.
About the NGC 6939
A rich, old open cluster that shares a frame with the Fireworks Galaxy. Cluster and galaxy in one shot.
Cep open cluster · Open cluster in Cepheus · magnitude 7.8 · 7′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Open clusters are the easiest targets in the sky. The stars are bright, so the aim is colour and tight stars rather than depth: short subs, no filter, and stop before the bright members saturate. The nominal time here gets you clean star colour; more integration only adds background stars.
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 6939 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 6939 with the ZWO Seestar S50: 6 min from Bortle 6
- NGC 6939 with the ZWO Seestar S50 Pro: 6 min from Bortle 6
- NGC 6939 with the ZWO Seestar S30: 6 min from Bortle 6
- NGC 6939 with the ZWO Seestar S30 Pro: 6 min from Bortle 6
- NGC 6939 with the DwarfLab DWARF 3: 8 min from Bortle 6
- NGC 6939 with the DwarfLab DWARF mini: 8 min from Bortle 6
- NGC 6939 with the DwarfLab Draco: 15 min from Bortle 6
- NGC 6939 with the DwarfLab DWARF II: 18 min from Bortle 6
- NGC 6939 with the Vaonis Vespera II: 6 min from Bortle 6
- NGC 6939 with the Vaonis Vespera Pro: 12 min from Bortle 6
- NGC 6939 with the Vaonis Vespera 3: 5 min from Bortle 6
- NGC 6939 with the Vaonis Vespera Pro 2: 12 min from Bortle 6
- NGC 6939 with the Unistellar eQuinox 2: 4 min from Bortle 6
- NGC 6939 with the Celestron Origin: 5 min from Bortle 6
- NGC 6939 with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the NGC 6939 · All targets for the Odyssey