How long to image the Iris Nebula with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 2 h 04 min (745 subs of 10 s) for a solid image of the Iris Nebula. A quick look takes 31 min; a showpiece 8 h 16 min. Under a Bortle 3 rural sky the solid figure drops to 48 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 | 10 min62 subs | 41 min245 subs | 2 h 43 min978 subs |
| Bortle 2Typical dark site | 11 min65 subs | 43 min260 subs | 2 h 53 min1,039 subs |
| Bortle 3Rural | 12 min73 subs | 48 min289 subs | 3 h 12 min1,155 subs |
| Bortle 4Rural / suburban transition | 15 min90 subs | 1 h360 subs | 3 h 59 min1,437 subs |
| Bortle 5Suburban | 20 min118 subs | 1 h 18 min471 subs | 5 h 14 min1,883 subs |
| Bortle 6Bright suburban | 31 min187 subs | 2 h 04 min745 subs | 8 h 16 min2,979 subs |
| Bortle 7Suburban / urban transition | 53 min317 subs | 3 h 31 min1,267 subs | 14 h5,066 subs |
| Bortle 8City | 1 h 27 min520 subs | 5 h 46 min2,077 subs | 23 h8,306 subs |
| Bortle 9Inner city | 2 h 39 min952 subs | 11 h3,805 subs | 42 h15,217 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 41 min of run time. The Seestar S50 Pro’s battery (rated about 9 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 30WAccepts 12 V 3 A PD, so a 30 W bank tops up the 10,000 mAh cell while imaging.
- Seestar S50 Pro dew shieldDew heater is built in; a shield adds margin on damp nights. Check the listing says S50 Pro.
- 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 S50 Pro →
How it frames
The Iris Nebula is 18′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 22% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 48 min289 subs | 1 h 18 min471 subs | 3 h 31 min1,267 subs |
| 20 s | 40 min122 subs | 1 h 11 min213 subs | 3 h 23 min611 subs |
| 30 s | 38 min76 subs | 1 h 08 min137 subs | 3 h 21 min402 subs |
| 60 s | 35 min36 subs | 1 h 06 min66 subs | 3 h 18 min199 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 12 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 S50 Pro
The S50 optics at 260 mm on an 8 MP 1/1.2-inch sensor: a wider, taller field, four times the pixels, and 60 s subs in EQ mode. Per pixel it is a whisker slower than the S50 because of the longer focal length; the long subs make it the better dark-site scope.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. 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 Iris Nebula from a Seestar S50 Pro? 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 S30: 1 h 59 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 S50 Pro