How long to image the Owl Cluster with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 5 min (30 subs of 10 s) for a solid image of the Owl Cluster. A quick look takes 2 min; a showpiece 15 min. Under a Bortle 3 rural sky the solid figure drops to 5 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 16% 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 | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 2Typical dark site | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 3Rural | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 4Rural / suburban transition | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 5Suburban | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 6Bright suburban | 2 min10 subs | 5 min30 subs | 15 min90 subs |
| Bortle 7Suburban / urban transition | 2 min10 subs | 5 min30 subs | 19 min113 subs |
| Bortle 8City | 2 min11 subs | 7 min42 subs | 28 min167 subs |
| Bortle 9Inner city | 3 min18 subs | 12 min71 subs | 47 min282 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 7 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 Owl Cluster is 13′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 16% 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 | 5 min30 subs | 5 min30 subs | 5 min30 subs |
| 20 s | 10 min30 subs | 10 min30 subs | 10 min30 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 15 min30 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
Leave the dual-band filter out for the Owl Cluster. It is an open cluster, 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 7 times slower.
About the Owl Cluster
Two bright stars for eyes and outstretched arms of fainter ones. A crowd-pleaser that needs only minutes.
NGC 457, Caldwell 13, ET Cluster · Open cluster in Cassiopeia · magnitude 6.4 · 13′ · best in Sep, Oct, Nov. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Open clusters are the easiest targets in the sky. The stars are bright, so the aim is colour and tight stars rather than depth: short subs, no filter, and stop before the bright members saturate. The nominal time here gets you clean star colour; more integration only adds background stars.
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 Owl Cluster 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
- Owl Cluster with the ZWO Seestar S50: 5 min from Bortle 6
- Owl Cluster with the ZWO Seestar S30: 5 min from Bortle 6
- Owl Cluster with the ZWO Seestar S30 Pro: 5 min from Bortle 6
- Owl Cluster with the DwarfLab DWARF 3: 8 min from Bortle 6
- Owl Cluster with the DwarfLab DWARF mini: 8 min from Bortle 6
- Owl Cluster with the DwarfLab Draco: 15 min from Bortle 6
- Owl Cluster with the DwarfLab DWARF II: 9 min from Bortle 6
- Owl Cluster with the Vaonis Vespera II: 5 min from Bortle 6
- Owl Cluster with the Vaonis Vespera Pro: 7 min from Bortle 6
- Owl Cluster with the Vaonis Vespera 3: 5 min from Bortle 6
- Owl Cluster with the Vaonis Vespera Pro 2: 6 min from Bortle 6
- Owl Cluster with the Unistellar eQuinox 2: 2 min from Bortle 6
- Owl Cluster with the Unistellar Odyssey: 10 min from Bortle 6
- Owl Cluster with the Celestron Origin: 5 min from Bortle 6
- Owl Cluster with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the Owl Cluster · All targets for the Seestar S50 Pro