How long to image the M68 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 2 h 08 min (1,916 subs of 4 s) for a solid image of the M68. A quick look takes 32 min; a showpiece 8 h 31 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 27 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 33% 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 | 21 min314 subs | 1 h 23 min1,253 subs | 5 h 34 min5,010 subs |
| Bortle 2Typical dark site | 21 min319 subs | 1 h 25 min1,273 subs | 5 h 39 min5,092 subs |
| Bortle 3Rural | 22 min328 subs | 1 h 27 min1,312 subs | 5 h 50 min5,246 subs |
| Bortle 4Rural / suburban transition | 23 min352 subs | 1 h 34 min1,405 subs | 6 h 15 min5,619 subs |
| Bortle 5Suburban | 26 min389 subs | 1 h 44 min1,553 subs | 6 h 54 min6,211 subs |
| Bortle 6Bright suburban | 32 min479 subs | 2 h 08 min1,916 subs | 8 h 31 min7,664 subs |
| Bortle 7Suburban / urban transition | 43 min652 subs | 2 h 54 min2,608 subs | 12 h10,431 subs |
| Bortle 8City | 1 h 01 min921 subs | 4 h 05 min3,682 subs | 16 h14,727 subs |
| Bortle 9Inner city | 1 h 40 min1,494 subs | 6 h 38 min5,973 subs | 27 h23,890 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 46 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 M68 is 11′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 33% of the frame’s short side.
About the M68
A loose globular in Hydra, low from the UK but easy from lower latitudes.
NGC 4590 · Globular cluster in Hydra · magnitude 7.8 · 11′ · best in Mar, Apr, May. 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 M68 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M68 with the ZWO Seestar S50: 32 min from Bortle 6
- M68 with the ZWO Seestar S50 Pro: 35 min from Bortle 6
- M68 with the ZWO Seestar S30: 33 min from Bortle 6
- M68 with the ZWO Seestar S30 Pro: 37 min from Bortle 6
- M68 with the DwarfLab DWARF 3: 46 min from Bortle 6
- M68 with the DwarfLab DWARF mini: 32 min from Bortle 6
- M68 with the DwarfLab Draco: 26 min from Bortle 6
- M68 with the DwarfLab DWARF II: 1 h 47 min from Bortle 6
- M68 with the Vaonis Vespera II: 32 min from Bortle 6
- M68 with the Vaonis Vespera Pro: 1 h 11 min from Bortle 6
- M68 with the Vaonis Vespera 3: 30 min from Bortle 6
- M68 with the Vaonis Vespera Pro 2: 1 h 07 min from Bortle 6
- M68 with the Unistellar eQuinox 2: 28 min from Bortle 6
- M68 with the Celestron Origin: 8 min from Bortle 6
- M68 with the Celestron Origin Mark II: 12 min from Bortle 6