How long to image the NGC 7331 with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 2 h 27 min (883 subs of 10 s) for a solid image of the NGC 7331. A quick look takes 37 min; a showpiece 9 h 48 min. Under a Bortle 3 rural sky the solid figure drops to 59 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 7% 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 | 13 min76 subs | 50 min302 subs | 3 h 21 min1,206 subs |
| Bortle 2Typical dark site | 13 min80 subs | 53 min320 subs | 3 h 33 min1,278 subs |
| Bortle 3Rural | 15 min89 subs | 59 min354 subs | 3 h 55 min1,413 subs |
| Bortle 4Rural / suburban transition | 18 min109 subs | 1 h 12 min435 subs | 4 h 50 min1,740 subs |
| Bortle 5Suburban | 24 min142 subs | 1 h 34 min565 subs | 6 h 16 min2,258 subs |
| Bortle 6Bright suburban | 37 min221 subs | 2 h 27 min883 subs | 9 h 48 min3,530 subs |
| Bortle 7Suburban / urban transition | 1 h 02 min373 subs | 4 h 08 min1,489 subs | 17 h5,954 subs |
| Bortle 8City | 1 h 41 min608 subs | 6 h 45 min2,430 subs | 27 h9,718 subs |
| Bortle 9Inner city | 3 h 05 min1,109 subs | 12 h4,436 subs | 49 h17,744 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 11 min of run time. The Seestar S30 Pro’s battery (rated about 5 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 power bank 10000mAh 5V 3A5 V 3 A input and it runs while charging.
- Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
- 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 Seestar S30 Pro →
How it frames
The NGC 7331 is 10′ × 4′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 7% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 59 min354 subs | 1 h 34 min565 subs | 4 h 08 min1,489 subs |
| 20 s | 49 min149 subs | 1 h 25 min255 subs | 3 h 59 min717 subs |
| 30 s | 46 min93 subs | 1 h 22 min164 subs | 3 h 56 min472 subs |
| 60 s | 43 min44 subs | 1 h 18 min79 subs | 3 h 52 min233 subs |
Leave the dual-band filter out for the NGC 7331. It is a galaxy, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 12 times slower.
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 ZWO Seestar S30 Pro
The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters on the telephoto camera.
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 60 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 Seestar S30 Pro? 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 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
- NGC 7331 with the Celestron Origin Mark II: 46 min from Bortle 6
All telescopes for the NGC 7331 · All targets for the Seestar S30 Pro