How long to image the NGC 7331 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 8 h 52 min (7,976 subs of 4 s) for a solid image of the NGC 7331. A quick look takes 2 h 13 min; a showpiece 35 h. Under a Bortle 3 rural sky the solid figure drops to 5 h 56 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 30% 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 | 1 h 25 min1,271 subs | 5 h 39 min5,081 subs | 23 h20,324 subs |
| Bortle 2Typical dark site | 1 h 26 min1,293 subs | 5 h 45 min5,170 subs | 23 h20,680 subs |
| Bortle 3Rural | 1 h 29 min1,335 subs | 5 h 56 min5,338 subs | 24 h21,352 subs |
| Bortle 4Rural / suburban transition | 1 h 36 min1,437 subs | 6 h 23 min5,746 subs | 26 h22,982 subs |
| Bortle 5Suburban | 1 h 47 min1,598 subs | 7 h 06 min6,392 subs | 28 h25,566 subs |
| Bortle 6Bright suburban | 2 h 13 min1,994 subs | 8 h 52 min7,976 subs | 35 h31,904 subs |
| Bortle 7Suburban / urban transition | 3 h 03 min2,749 subs | 12 h10,996 subs | 49 h43,982 subs |
| Bortle 8City | 4 h 21 min3,921 subs | 17 h15,684 subs | 70 h62,734 subs |
| Bortle 9Inner city | 7 h 08 min6,421 subs | 29 h25,682 subs | 110+ h102,727 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 12 h of run time. That is more than one night: over 2 nights, about 5 h 46 min each. The Odyssey’s battery is rated at about 5 h, so each night needs an external power bank. (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.
Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.
Everything that fits the Odyssey →
How it frames
The NGC 7331 is 10′ × 4′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 30% of the frame’s short side.
About the NGC 7331
A tilted spiral often compared to the Milky Way, with a group of background galaxies alongside. Stephan's Quintet is half a degree away.
Caldwell 30 · Galaxy in Pegasus · magnitude 9.5 · 10′ × 4′ · best in Aug, Sep, Oct. 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 NGC 7331 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 7331 with the ZWO Seestar S50: 2 h 07 min from Bortle 6
- NGC 7331 with the ZWO Seestar S50 Pro: 2 h 19 min from Bortle 6
- NGC 7331 with the ZWO Seestar S30: 2 h 13 min from Bortle 6
- NGC 7331 with the ZWO Seestar S30 Pro: 2 h 27 min from Bortle 6
- NGC 7331 with the DwarfLab DWARF 3: 3 h 04 min from Bortle 6
- NGC 7331 with the DwarfLab DWARF mini: 2 h 06 min from Bortle 6
- NGC 7331 with the DwarfLab Draco: 1 h 44 min from Bortle 6
- NGC 7331 with the DwarfLab DWARF II: 7 h 14 min from Bortle 6
- NGC 7331 with the Vaonis Vespera II: 2 h 07 min from Bortle 6
- NGC 7331 with the Vaonis Vespera Pro: 4 h 44 min from Bortle 6
- NGC 7331 with the Vaonis Vespera 3: 2 h 01 min from Bortle 6
- NGC 7331 with the Vaonis Vespera Pro 2: 4 h 31 min from Bortle 6
- NGC 7331 with the Unistellar eQuinox 2: 1 h 55 min from Bortle 6
- NGC 7331 with the Celestron Origin: 34 min from Bortle 6
- NGC 7331 with the Celestron Origin Mark II: 46 min from Bortle 6
All telescopes for the NGC 7331 · All targets for the Odyssey