How long to image the California Nebula with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 2 h (720 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the California Nebula. A quick look takes 30 min; a showpiece 8 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 23 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is 3.7× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 20 min119 subs | 1 h 19 min474 subs | 5 h 15 min1,893 subs |
| Bortle 2Typical dark site | 20 min121 subs | 1 h 20 min481 subs | 5 h 21 min1,924 subs |
| Bortle 3Rural | 21 min124 subs | 1 h 23 min496 subs | 5 h 30 min1,981 subs |
| Bortle 4Rural / suburban transition | 22 min133 subs | 1 h 28 min530 subs | 5 h 53 min2,119 subs |
| Bortle 5Suburban | 24 min147 subs | 1 h 37 min585 subs | 6 h 30 min2,339 subs |
| Bortle 6Bright suburban | 30 min180 subs | 2 h720 subs | 8 h2,878 subs |
| Bortle 7Suburban / urban transition | 41 min244 subs | 2 h 43 min976 subs | 11 h3,904 subs |
| Bortle 8City | 57 min344 subs | 3 h 49 min1,375 subs | 15 h5,498 subs |
| Bortle 9Inner city | 1 h 33 min557 subs | 6 h 11 min2,225 subs | 25 h8,897 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 36 min of run time. The Seestar S50’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, and 30% off the battery for a December night.)
- USB-C power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
- Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks stray light.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the Seestar S50 →
How it frames
The California Nebula is 160′ × 40′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is 3.7× wider than the frame. A mosaic, or choosing the part you want and letting the rest go, is how it gets shot on this scope.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 1 h 23 min496 subs | 1 h 37 min585 subs | 2 h 43 min976 subs |
| 20 s | 59 min178 subs | 1 h 14 min223 subs | 2 h 19 min419 subs |
| 30 s | 51 min103 subs | 1 h 06 min133 subs | 2 h 12 min264 subs |
| 60 s | 44 min44 subs | 59 min59 subs | 2 h 04 min124 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 1 h 11 min429 subs | 2 h721 subs | 5 h 33 min1,999 subs |
| dual-band (LP filter) | 1 h 23 min496 subs | 1 h 37 min585 subs | 2 h 43 min976 subs |
About the California Nebula
A long, faint hydrogen streak near Menkib, nearly three degrees end to end. Needs a wide field and a dual-band filter; it is almost invisible in broadband.
NGC 1499 · Emission nebula in Perseus · magnitude 6.0 · 160′ × 40′ · best in Nov, Dec, Jan. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.
Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.
About the ZWO Seestar S50
The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.
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 California Nebula from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- California Nebula with the ZWO Seestar S50 Pro: 2 h 15 min from Bortle 6
- California Nebula with the ZWO Seestar S30: 2 h 20 min from Bortle 6
- California Nebula with the ZWO Seestar S30 Pro: 2 h 25 min from Bortle 6
- California Nebula with the DwarfLab DWARF 3: 2 h 28 min from Bortle 6
- California Nebula with the DwarfLab DWARF mini: 1 h 58 min from Bortle 6
- California Nebula with the DwarfLab Draco: 1 h 35 min from Bortle 6
- California Nebula with the DwarfLab DWARF II: 11 h from Bortle 6
- California Nebula with the Vaonis Vespera II: 3 h 13 min from Bortle 6
- California Nebula with the Vaonis Vespera Pro: 7 h 14 min from Bortle 6
- California Nebula with the Vaonis Vespera 3: 3 h 05 min from Bortle 6
- California Nebula with the Vaonis Vespera Pro 2: 6 h 53 min from Bortle 6
- California Nebula with the Unistellar eQuinox 2: 2 h 57 min from Bortle 6
- California Nebula with the Unistellar Odyssey: 14 h from Bortle 6
- California Nebula with the Celestron Origin: 51 min from Bortle 6
- California Nebula with the Celestron Origin Mark II: 1 h 10 min from Bortle 6
All telescopes for the California Nebula · All targets for the Seestar S50