How long to image the M39 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 9 min (136 subs of 4 s) for a solid image of the M39. A quick look takes 2 min; a showpiece 36 min. Under a Bortle 3 rural sky the solid figure drops to 7 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it only just fits, at 95% of the short side.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 2 min25 subs | 7 min98 subs | 26 min391 subs |
| Bortle 2Typical dark site | 2 min25 subs | 7 min99 subs | 26 min396 subs |
| Bortle 3Rural | 2 min26 subs | 7 min102 subs | 27 min405 subs |
| Bortle 4Rural / suburban transition | 2 min27 subs | 7 min107 subs | 28 min426 subs |
| Bortle 5Suburban | 2 min29 subs | 8 min115 subs | 31 min460 subs |
| Bortle 6Bright suburban | 2 min34 subs | 9 min136 subs | 36 min543 subs |
| Bortle 7Suburban / urban transition | 3 min44 subs | 12 min176 subs | 47 min701 subs |
| Bortle 8City | 4 min60 subs | 16 min237 subs | 1 h 03 min947 subs |
| Bortle 9Inner city | 6 min92 subs | 24 min368 subs | 1 h 38 min1,470 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 12 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 M39 is 32′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it only just fits, at 95% of the short side. Centre it carefully: there is no room to crop back afterwards.
About the M39
A large, sparse triangle of bright stars in northern Cygnus. Quick and pretty.
NGC 7092 · Open cluster in Cygnus · magnitude 4.6 · 32′ · 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 M39 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M39 with the ZWO Seestar S50: 5 min from Bortle 6
- M39 with the ZWO Seestar S50 Pro: 5 min from Bortle 6
- M39 with the ZWO Seestar S30: 5 min from Bortle 6
- M39 with the ZWO Seestar S30 Pro: 5 min from Bortle 6
- M39 with the DwarfLab DWARF 3: 8 min from Bortle 6
- M39 with the DwarfLab DWARF mini: 8 min from Bortle 6
- M39 with the DwarfLab Draco: 15 min from Bortle 6
- M39 with the DwarfLab DWARF II: 8 min from Bortle 6
- M39 with the Vaonis Vespera II: 5 min from Bortle 6
- M39 with the Vaonis Vespera Pro: 6 min from Bortle 6
- M39 with the Vaonis Vespera 3: 5 min from Bortle 6
- M39 with the Vaonis Vespera Pro 2: 5 min from Bortle 6
- M39 with the Unistellar eQuinox 2: 2 min from Bortle 6
- M39 with the Celestron Origin: 5 min from Bortle 6
- M39 with the Celestron Origin Mark II: 5 min from Bortle 6