How long to image the M108 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 5 h 57 min (5,355 subs of 4 s) for a solid image of the M108. A quick look takes 1 h 29 min; a showpiece 24 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 01 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 26% 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 | 57 min861 subs | 3 h 49 min3,441 subs | 15 h13,763 subs |
| Bortle 2Typical dark site | 58 min875 subs | 3 h 53 min3,500 subs | 16 h13,998 subs |
| Bortle 3Rural | 1 h903 subs | 4 h 01 min3,611 subs | 16 h14,443 subs |
| Bortle 4Rural / suburban transition | 1 h 05 min971 subs | 4 h 19 min3,881 subs | 17 h15,521 subs |
| Bortle 5Suburban | 1 h 12 min1,077 subs | 4 h 47 min4,307 subs | 19 h17,228 subs |
| Bortle 6Bright suburban | 1 h 29 min1,339 subs | 5 h 57 min5,355 subs | 24 h21,418 subs |
| Bortle 7Suburban / urban transition | 2 h 03 min1,838 subs | 8 h 10 min7,351 subs | 33 h29,403 subs |
| Bortle 8City | 2 h 54 min2,613 subs | 12 h10,450 subs | 46 h41,799 subs |
| Bortle 9Inner city | 4 h 44 min4,265 subs | 19 h17,060 subs | 76 h68,237 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 7 h 44 min of run time. That is more than one night: over 2 nights, about 3 h 52 min each. The Odyssey’s battery (rated about 5 h) should cover each night; 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 M108 is 8.7′ × 2.2′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 26% of the frame’s short side.
About the M108
An edge-on spiral with a mottled, dusty disc, a degree from the Owl Nebula. Frame both together.
NGC 3556 · Galaxy in Ursa Major · magnitude 10.0 · 8.7′ × 2.2′ · best in Feb, Mar, Apr. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.
Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.
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 M108 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M108 with the ZWO Seestar S50: 1 h 26 min from Bortle 6
- M108 with the ZWO Seestar S50 Pro: 1 h 34 min from Bortle 6
- M108 with the ZWO Seestar S30: 1 h 30 min from Bortle 6
- M108 with the ZWO Seestar S30 Pro: 1 h 40 min from Bortle 6
- M108 with the DwarfLab DWARF 3: 2 h 06 min from Bortle 6
- M108 with the DwarfLab DWARF mini: 1 h 26 min from Bortle 6
- M108 with the DwarfLab Draco: 1 h 11 min from Bortle 6
- M108 with the DwarfLab DWARF II: 4 h 54 min from Bortle 6
- M108 with the Vaonis Vespera II: 1 h 26 min from Bortle 6
- M108 with the Vaonis Vespera Pro: 3 h 13 min from Bortle 6
- M108 with the Vaonis Vespera 3: 1 h 22 min from Bortle 6
- M108 with the Vaonis Vespera Pro 2: 3 h 04 min from Bortle 6
- M108 with the Unistellar eQuinox 2: 1 h 18 min from Bortle 6
- M108 with the Celestron Origin: 23 min from Bortle 6
- M108 with the Celestron Origin Mark II: 31 min from Bortle 6