How long to image the M18 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 15 min (227 subs of 4 s) for a solid image of the M18. A quick look takes 4 min; a showpiece 1 h. Under a Bortle 3 rural sky the solid figure drops to 11 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 27% 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 min41 subs | 11 min163 subs | 43 min652 subs |
| Bortle 2Typical dark site | 3 min42 subs | 11 min165 subs | 44 min660 subs |
| Bortle 3Rural | 3 min43 subs | 11 min169 subs | 45 min675 subs |
| Bortle 4Rural / suburban transition | 3 min45 subs | 12 min178 subs | 47 min710 subs |
| Bortle 5Suburban | 3 min48 subs | 13 min192 subs | 51 min766 subs |
| Bortle 6Bright suburban | 4 min57 subs | 15 min227 subs | 1 h905 subs |
| Bortle 7Suburban / urban transition | 5 min73 subs | 19 min292 subs | 1 h 18 min1,168 subs |
| Bortle 8City | 7 min99 subs | 26 min395 subs | 1 h 45 min1,578 subs |
| Bortle 9Inner city | 10 min154 subs | 41 min613 subs | 2 h 43 min2,450 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 20 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 M18 is 9′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 27% of the frame’s short side.
About the M18
A small, sparse open cluster just south of the Omega Nebula. Usually caught in the same frame.
NGC 6613 · Open cluster in Sagittarius · magnitude 6.9 · 9′ · best in Jun, Jul, Aug. 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 M18 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M18 with the ZWO Seestar S50: 5 min from Bortle 6
- M18 with the ZWO Seestar S50 Pro: 5 min from Bortle 6
- M18 with the ZWO Seestar S30: 5 min from Bortle 6
- M18 with the ZWO Seestar S30 Pro: 5 min from Bortle 6
- M18 with the DwarfLab DWARF 3: 8 min from Bortle 6
- M18 with the DwarfLab DWARF mini: 8 min from Bortle 6
- M18 with the DwarfLab Draco: 15 min from Bortle 6
- M18 with the DwarfLab DWARF II: 14 min from Bortle 6
- M18 with the Vaonis Vespera II: 5 min from Bortle 6
- M18 with the Vaonis Vespera Pro: 9 min from Bortle 6
- M18 with the Vaonis Vespera 3: 5 min from Bortle 6
- M18 with the Vaonis Vespera Pro 2: 9 min from Bortle 6
- M18 with the Unistellar eQuinox 2: 3 min from Bortle 6
- M18 with the Celestron Origin: 5 min from Bortle 6
- M18 with the Celestron Origin Mark II: 5 min from Bortle 6