How long to image the Pleiades with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 2 h 57 min (1,063 subs of 10 s) for a solid image of the Pleiades. A quick look takes 44 min; a showpiece 12 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 07 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 is just over the frame at 1.3×.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 14 min85 subs | 57 min340 subs | 3 h 46 min1,357 subs |
| Bortle 2Typical dark site | 15 min91 subs | 1 h362 subs | 4 h 01 min1,446 subs |
| Bortle 3Rural | 17 min101 subs | 1 h 07 min404 subs | 4 h 29 min1,614 subs |
| Bortle 4Rural / suburban transition | 21 min127 subs | 1 h 24 min506 subs | 5 h 37 min2,021 subs |
| Bortle 5Suburban | 28 min167 subs | 1 h 51 min667 subs | 7 h 24 min2,666 subs |
| Bortle 6Bright suburban | 44 min266 subs | 2 h 57 min1,063 subs | 12 h4,249 subs |
| Bortle 7Suburban / urban transition | 1 h 16 min455 subs | 5 h 03 min1,817 subs | 20 h7,266 subs |
| Bortle 8City | 2 h 04 min747 subs | 8 h 18 min2,988 subs | 33 h11,950 subs |
| Bortle 9Inner city | 3 h 49 min1,372 subs | 15 h5,485 subs | 61 h21,939 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 50 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, and 30% off the battery for a November night.)
- 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.
- 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 Pro →
How it frames
The Pleiades is 110′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it is just over the frame at 1.3×. Point at the part you want; the edges will fall outside the frame.
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 | 1 h 07 min404 subs | 1 h 51 min667 subs | 5 h 03 min1,817 subs |
| 20 s | 56 min169 subs | 1 h 40 min300 subs | 4 h 52 min875 subs |
| 30 s | 52 min105 subs | 1 h 36 min193 subs | 4 h 48 min576 subs |
| 60 s | 49 min49 subs | 1 h 33 min93 subs | 4 h 44 min285 subs |
Leave the dual-band filter out for the Pleiades. 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 Pleiades
The stars take seconds. The blue reflection nebulosity around them is faint and needs hours from any sky, and no filter helps because it is starlight, not emission.
M45, Seven Sisters · Reflection nebula in Taurus · magnitude 1.6 · 110′ · best in Oct, Nov, Dec. 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 Pleiades 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
- Pleiades with the ZWO Seestar S50: 2 h 42 min from Bortle 6
- Pleiades with the ZWO Seestar S30: 2 h 50 min from Bortle 6
- Pleiades with the ZWO Seestar S30 Pro: 3 h 08 min from Bortle 6
- Pleiades with the DwarfLab DWARF 3: 3 h 55 min from Bortle 6
- Pleiades with the DwarfLab DWARF mini: 2 h 41 min from Bortle 6
- Pleiades with the DwarfLab Draco: 2 h 13 min from Bortle 6
- Pleiades with the DwarfLab DWARF II: 9 h 16 min from Bortle 6
- Pleiades with the Vaonis Vespera II: 2 h 42 min from Bortle 6
- Pleiades with the Vaonis Vespera Pro: 6 h 03 min from Bortle 6
- Pleiades with the Vaonis Vespera 3: 2 h 35 min from Bortle 6
- Pleiades with the Vaonis Vespera Pro 2: 5 h 46 min from Bortle 6
- Pleiades with the Unistellar eQuinox 2: 2 h 28 min from Bortle 6
- Pleiades with the Unistellar Odyssey: 11 h from Bortle 6
- Pleiades with the Celestron Origin: 43 min from Bortle 6
- Pleiades with the Celestron Origin Mark II: 59 min from Bortle 6
All telescopes for the Pleiades · All targets for the Seestar S50 Pro