How long to image the NGC 7331 with the Celestron Origin Mark II
From a Bortle 6 suburban sky, the Celestron Origin Mark II needs about 46 min (277 subs of 10 s) for a solid image of the NGC 7331. A quick look takes 12 min; a showpiece 3 h 04 min. Under a Bortle 3 rural sky the solid figure drops to 14 min. At Bortle 6 the limit is skyglow, so a darker site or a filter helps more than longer subs. In this scope's field it fills 22% 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 | 3 min17 subs | 11 min68 subs | 45 min272 subs |
| Bortle 2Typical dark site | 3 min19 subs | 12 min75 subs | 49 min297 subs |
| Bortle 3Rural | 4 min22 subs | 14 min87 subs | 58 min346 subs |
| Bortle 4Rural / suburban transition | 5 min29 subs | 19 min116 subs | 1 h 17 min463 subs |
| Bortle 5Suburban | 7 min41 subs | 27 min163 subs | 1 h 48 min649 subs |
| Bortle 6Bright suburban | 12 min70 subs | 46 min277 subs | 3 h 04 min1,106 subs |
| Bortle 7Suburban / urban transition | 21 min124 subs | 1 h 22 min494 subs | 5 h 29 min1,976 subs |
| Bortle 8City | 35 min208 subs | 2 h 19 min832 subs | 9 h 15 min3,328 subs |
| Bortle 9Inner city | 1 h 05 min389 subs | 4 h 19 min1,553 subs | 17 h6,210 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h of run time. The Origin Mark II’s battery (rated about 6 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.)
- portable power station 300W AC outletRuns the supplied 12 V adapter off-grid; dew shield and heater are built in.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames
The NGC 7331 is 10′ × 4′ across. The Origin Mark II frames 1.32° × 0.75° at 1.23″ per pixel, so it fills 22% of the frame’s short side.
Longer subs
10 s auto subs (15 s with the Nebula Filter); manual 1 to 30 s on the alt-az mount, longer only with the EQ wedge, and 60 s and up needs the StarSense Autoguider too. Celestron warns the f/2.2 optics saturate quickly without the filter. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 14 min87 subs | 27 min163 subs | 1 h 22 min494 subs |
| 15 s | 14 min57 subs | 27 min108 subs | 1 h 22 min329 subs |
| 30 s | 15 min30 subs | 26 min53 subs | 1 h 22 min164 subs |
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 Celestron Origin Mark II
The Origin Mark II (late 2025): the same 6-inch f/2.2 RASA with an 8 MP IMX678 in place of the original 6 MP IMX178. Smaller pixels for finer detail, a quieter sensor, and still the fastest system here by a wide margin.
10 s auto subs (15 s with the Nebula Filter); manual 1 to 30 s on the alt-az mount, longer only with the EQ wedge, and 60 s and up needs the StarSense Autoguider too. Celestron warns the f/2.2 optics saturate quickly without the filter. Filter drawer takes 1.25-inch or 2-inch filters, including dual-band; Celestron sells an optional Nebula Filter.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 s and 30 s subs is small; from a rural site it can halve the total time, especially with a dual-band filter in place.
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 Origin Mark II? 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 Unistellar Odyssey: 8 h 52 min from Bortle 6
- NGC 7331 with the Celestron Origin: 34 min from Bortle 6
All telescopes for the NGC 7331 · All targets for the Origin Mark II