How long to image the NGC 7331 with the Vaonis Vespera II
From a Bortle 6 suburban sky, the Vaonis Vespera II needs about 2 h 07 min (762 subs of 10 s) for a solid image of the NGC 7331. A quick look takes 32 min; a showpiece 8 h 27 min. Under a Bortle 3 rural sky the solid figure drops to 49 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 12% 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 | 10 min63 subs | 42 min251 subs | 2 h 47 min1,003 subs |
| Bortle 2Typical dark site | 11 min67 subs | 44 min267 subs | 2 h 57 min1,065 subs |
| Bortle 3Rural | 12 min74 subs | 49 min296 subs | 3 h 17 min1,184 subs |
| Bortle 4Rural / suburban transition | 15 min92 subs | 1 h 01 min368 subs | 4 h 05 min1,472 subs |
| Bortle 5Suburban | 20 min121 subs | 1 h 20 min482 subs | 5 h 21 min1,927 subs |
| Bortle 6Bright suburban | 32 min191 subs | 2 h 07 min762 subs | 8 h 27 min3,045 subs |
| Bortle 7Suburban / urban transition | 54 min324 subs | 3 h 36 min1,294 subs | 14 h5,176 subs |
| Bortle 8City | 1 h 28 min531 subs | 5 h 53 min2,121 subs | 24 h8,484 subs |
| Bortle 9Inner city | 2 h 42 min972 subs | 11 h3,885 subs | 43 h15,538 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 45 min of run time. The Vespera II’s battery (rated about 4 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-C PD power bank 20000mAh 30WOnly four hours inside; Vaonis specifies a 30 W PD source. C-to-C cable not included.
- Vaonis Vespera hygrometer sensorTriggers the built-in demister automatically; the correct dew accessory for the II.
- 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 Vespera II frames 2.55° × 1.44° at 2.39″ per pixel, so it fills 12% of the frame’s short side.
Longer subs
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 49 min296 subs | 1 h 20 min482 subs | 3 h 36 min1,294 subs |
| 20 s | 42 min127 subs | 1 h 13 min220 subs | 3 h 28 min626 subs |
| 30 s | 40 min80 subs | 1 h 11 min142 subs | 3 h 26 min412 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 Vaonis Vespera II
A 50 mm quadruplet on an 8 MP sensor with Vaonis’s mosaic mode for wide fields. Same optics class as the Seestar S50, four times the pixels.
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar; the app detects which is fitted.
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 Vespera 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 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
- NGC 7331 with the Celestron Origin Mark II: 46 min from Bortle 6
All telescopes for the NGC 7331 · All targets for the Vespera II