How long to image the Iris Nebula with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 1 h 59 min (716 subs of 10 s) for a solid image of the Iris Nebula. A quick look takes 30 min; a showpiece 7 h 57 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 25% 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 | 11 min64 subs | 42 min253 subs | 2 h 49 min1,012 subs |
| Bortle 2Typical dark site | 11 min67 subs | 45 min268 subs | 2 h 58 min1,069 subs |
| Bortle 3Rural | 12 min74 subs | 49 min294 subs | 3 h 16 min1,176 subs |
| Bortle 4Rural / suburban transition | 15 min90 subs | 1 h359 subs | 3 h 59 min1,436 subs |
| Bortle 5Suburban | 19 min116 subs | 1 h 17 min463 subs | 5 h 08 min1,849 subs |
| Bortle 6Bright suburban | 30 min179 subs | 1 h 59 min716 subs | 7 h 57 min2,862 subs |
| Bortle 7Suburban / urban transition | 50 min300 subs | 3 h 20 min1,198 subs | 13 h4,791 subs |
| Bortle 8City | 1 h 21 min487 subs | 5 h 24 min1,947 subs | 22 h7,787 subs |
| Bortle 9Inner city | 2 h 28 min887 subs | 9 h 51 min3,545 subs | 39 h14,177 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 35 min of run time. The Seestar S30’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.)
- USB-C power bank 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
- Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and stray light.
- 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 →
How it frames
The Iris Nebula is 18′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 25% 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 | 49 min294 subs | 1 h 17 min463 subs | 3 h 20 min1,198 subs |
| 20 s | 40 min119 subs | 1 h 08 min203 subs | 3 h 10 min571 subs |
| 30 s | 36 min73 subs | 1 h 04 min129 subs | 3 h 07 min375 subs |
| 60 s | 33 min34 subs | 1 h 01 min62 subs | 3 h 04 min184 subs |
Leave the dual-band filter out for the Iris Nebula. It is a reflection nebula, 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 13 times slower.
About the Iris Nebula
A blue reflection nebula wrapped in dark dust. No filter helps, and the surrounding dust needs a dark sky and hours.
NGC 7023, Caldwell 4 · Reflection nebula in Cepheus · magnitude 6.8 · 18′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.
About the ZWO Seestar S30
Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.
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.
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 Iris Nebula from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Iris Nebula with the ZWO Seestar S50: 1 h 53 min from Bortle 6
- Iris Nebula with the ZWO Seestar S50 Pro: 2 h 04 min from Bortle 6
- Iris Nebula with the ZWO Seestar S30 Pro: 2 h 12 min from Bortle 6
- Iris Nebula with the DwarfLab DWARF 3: 2 h 45 min from Bortle 6
- Iris Nebula with the DwarfLab DWARF mini: 1 h 53 min from Bortle 6
- Iris Nebula with the DwarfLab Draco: 1 h 33 min from Bortle 6
- Iris Nebula with the DwarfLab DWARF II: 6 h 29 min from Bortle 6
- Iris Nebula with the Vaonis Vespera II: 1 h 53 min from Bortle 6
- Iris Nebula with the Vaonis Vespera Pro: 4 h 14 min from Bortle 6
- Iris Nebula with the Vaonis Vespera 3: 1 h 48 min from Bortle 6
- Iris Nebula with the Vaonis Vespera Pro 2: 4 h 02 min from Bortle 6
- Iris Nebula with the Unistellar eQuinox 2: 1 h 43 min from Bortle 6
- Iris Nebula with the Unistellar Odyssey: 7 h 58 min from Bortle 6
- Iris Nebula with the Celestron Origin: 30 min from Bortle 6
- Iris Nebula with the Celestron Origin Mark II: 41 min from Bortle 6
All telescopes for the Iris Nebula · All targets for the Seestar S30