How long to image the M55 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 54 min (814 subs of 4 s) for a solid image of the M55. A quick look takes 14 min; a showpiece 3 h 37 min. Under a Bortle 3 rural sky the solid figure drops to 38 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 56% 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 | 9 min136 subs | 36 min541 subs | 2 h 24 min2,162 subs |
| Bortle 2Typical dark site | 9 min138 subs | 37 min549 subs | 2 h 26 min2,195 subs |
| Bortle 3Rural | 9 min142 subs | 38 min565 subs | 2 h 31 min2,259 subs |
| Bortle 4Rural / suburban transition | 10 min151 subs | 40 min603 subs | 2 h 41 min2,412 subs |
| Bortle 5Suburban | 11 min166 subs | 44 min664 subs | 2 h 57 min2,656 subs |
| Bortle 6Bright suburban | 14 min204 subs | 54 min814 subs | 3 h 37 min3,254 subs |
| Bortle 7Suburban / urban transition | 18 min275 subs | 1 h 13 min1,099 subs | 4 h 53 min4,394 subs |
| Bortle 8City | 26 min386 subs | 1 h 43 min1,541 subs | 6 h 51 min6,164 subs |
| Bortle 9Inner city | 41 min622 subs | 2 h 46 min2,485 subs | 11 h9,937 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 10 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 M55 is 19′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 56% of the frame’s short side.
About the M55
A large, loose globular that resolves easily but sits low for northern imagers.
NGC 6809 · Globular cluster in Sagittarius · magnitude 6.3 · 19′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.
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 M55 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M55 with the ZWO Seestar S50: 14 min from Bortle 6
- M55 with the ZWO Seestar S50 Pro: 15 min from Bortle 6
- M55 with the ZWO Seestar S30: 14 min from Bortle 6
- M55 with the ZWO Seestar S30 Pro: 16 min from Bortle 6
- M55 with the DwarfLab DWARF 3: 20 min from Bortle 6
- M55 with the DwarfLab DWARF mini: 14 min from Bortle 6
- M55 with the DwarfLab Draco: 15 min from Bortle 6
- M55 with the DwarfLab DWARF II: 46 min from Bortle 6
- M55 with the Vaonis Vespera II: 14 min from Bortle 6
- M55 with the Vaonis Vespera Pro: 31 min from Bortle 6
- M55 with the Vaonis Vespera 3: 13 min from Bortle 6
- M55 with the Vaonis Vespera Pro 2: 29 min from Bortle 6
- M55 with the Unistellar eQuinox 2: 12 min from Bortle 6
- M55 with the Celestron Origin: 5 min from Bortle 6
- M55 with the Celestron Origin Mark II: 5 min from Bortle 6