NGC 7331
Caldwell 30 · Galaxy in Pegasus
- Magnitude
- 9.5
- Size
- 10′ × 4′
- Effective surface brightness
- 22.1 mag/arcsec²
- Best months
- Aug, Sep, Oct
- Declination
- +34°
- Filter
- None (broadband target)
A tilted spiral often compared to the Milky Way, with a group of background galaxies alongside. Stephan's Quintet is half a degree away.
Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
How long with each smart telescope
| Telescope | In frame | Bortle 3 (rural) | Bortle 5 (suburban) | Bortle 7 (urban edge) |
|---|---|---|---|---|
| ZWO Seestar S5010 s subs | 23% | 49 min296 subs | 1 h 20 min482 subs | 3 h 36 min1,294 subs |
| ZWO Seestar S50 Pro10 s subs | 12% | 55 min330 subs | 1 h 28 min531 subs | 3 h 55 min1,409 subs |
| ZWO Seestar S3010 s subs | 14% | 56 min335 subs | 1 h 27 min521 subs | 3 h 42 min1,333 subs |
| ZWO Seestar S30 Pro10 s subs | 7% | 59 min354 subs | 1 h 34 min565 subs | 4 h 08 min1,489 subs |
| DwarfLab DWARF 315 s subs | 10% | 1 h 05 min259 subs | 1 h 52 min450 subs | 5 h 21 min1,286 subs |
| DwarfLab DWARF mini15 s subs | 14% | 49 min195 subs | 1 h 20 min319 subs | 3 h 35 min861 subs |
| DwarfLab Draco30 s subs | 13% | 39 min79 subs | 1 h 05 min131 subs | 2 h 58 min357 subs |
| DwarfLab DWARF II15 s subs | 9% | 3 h 38 min874 subs | 5 h 05 min1,219 subs | 11 h2,722 subs |
| Vaonis Vespera II10 s subs | 12% | 49 min296 subs | 1 h 20 min482 subs | 3 h 36 min1,294 subs |
| Vaonis Vespera Pro10 s subs | 10% | 2 h 01 min726 subs | 3 h 06 min1,117 subs | 7 h 51 min2,824 subs |
| Vaonis Vespera 310 s subs | 11% | 47 min281 subs | 1 h 16 min459 subs | 3 h 26 min1,239 subs |
| Vaonis Vespera Pro 210 s subs | 10% | 1 h 54 min685 subs | 2 h 57 min1,060 subs | 7 h 30 min2,700 subs |
| Unistellar eQuinox 24 s subs | 29% | 1 h 07 min1,000 subs | 1 h 26 min1,290 subs | 2 h 50 min2,555 subs |
| Unistellar Odyssey4 s subs | 30% | 5 h 56 min5,338 subs | 7 h 06 min6,392 subs | 12 h10,996 subs |
| Celestron Origin10 s subs | 20% | 12 min70 subs | 20 min123 subs | 59 min353 subs |
| Celestron Origin Mark II10 s subs | 22% | 14 min87 subs | 27 min163 subs | 1 h 22 min494 subs |
Imaging the galaxy
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.
Per-telescope pages
- How long to image the NGC 7331 with the ZWO Seestar S50
- How long to image the NGC 7331 with the ZWO Seestar S50 Pro
- How long to image the NGC 7331 with the ZWO Seestar S30
- How long to image the NGC 7331 with the ZWO Seestar S30 Pro
- How long to image the NGC 7331 with the DwarfLab DWARF 3
- How long to image the NGC 7331 with the DwarfLab DWARF mini
- How long to image the NGC 7331 with the DwarfLab Draco
- How long to image the NGC 7331 with the DwarfLab DWARF II
- How long to image the NGC 7331 with the Vaonis Vespera II
- How long to image the NGC 7331 with the Vaonis Vespera Pro
- How long to image the NGC 7331 with the Vaonis Vespera 3
- How long to image the NGC 7331 with the Vaonis Vespera Pro 2
- How long to image the NGC 7331 with the Unistellar eQuinox 2
- How long to image the NGC 7331 with the Unistellar Odyssey
- How long to image the NGC 7331 with the Celestron Origin
- How long to image the NGC 7331 with the Celestron Origin Mark II