How long to image the M28 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 23 min (347 subs of 4 s) for a solid image of the M28. A quick look takes 6 min; a showpiece 1 h 32 min. Under a Bortle 3 rural sky the solid figure drops to 17 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 | 4 min61 subs | 16 min242 subs | 1 h 04 min965 subs |
| Bortle 2Typical dark site | 4 min62 subs | 16 min245 subs | 1 h 05 min977 subs |
| Bortle 3Rural | 4 min63 subs | 17 min251 subs | 1 h 07 min1,002 subs |
| Bortle 4Rural / suburban transition | 4 min67 subs | 18 min266 subs | 1 h 11 min1,061 subs |
| Bortle 5Suburban | 5 min73 subs | 19 min289 subs | 1 h 17 min1,155 subs |
| Bortle 6Bright suburban | 6 min87 subs | 23 min347 subs | 1 h 32 min1,385 subs |
| Bortle 7Suburban / urban transition | 8 min114 subs | 30 min456 subs | 2 h 02 min1,824 subs |
| Bortle 8City | 10 min157 subs | 42 min627 subs | 2 h 47 min2,505 subs |
| Bortle 9Inner city | 16 min248 subs | 1 h 06 min990 subs | 4 h 24 min3,957 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 30 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 M28 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 M28
A compact globular near Lambda Sagittarii, a degree from M22. Small and quick.
NGC 6626 · Globular cluster in Sagittarius · magnitude 6.8 · 11′ · 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 M28 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M28 with the ZWO Seestar S50: 6 min from Bortle 6
- M28 with the ZWO Seestar S50 Pro: 7 min from Bortle 6
- M28 with the ZWO Seestar S30: 7 min from Bortle 6
- M28 with the ZWO Seestar S30 Pro: 7 min from Bortle 6
- M28 with the DwarfLab DWARF 3: 9 min from Bortle 6
- M28 with the DwarfLab DWARF mini: 8 min from Bortle 6
- M28 with the DwarfLab Draco: 15 min from Bortle 6
- M28 with the DwarfLab DWARF II: 20 min from Bortle 6
- M28 with the Vaonis Vespera II: 6 min from Bortle 6
- M28 with the Vaonis Vespera Pro: 14 min from Bortle 6
- M28 with the Vaonis Vespera 3: 6 min from Bortle 6
- M28 with the Vaonis Vespera Pro 2: 13 min from Bortle 6
- M28 with the Unistellar eQuinox 2: 5 min from Bortle 6
- M28 with the Celestron Origin: 5 min from Bortle 6
- M28 with the Celestron Origin Mark II: 5 min from Bortle 6