How long to image the Little Dumbbell with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 36 min (218 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Little Dumbbell. A quick look takes 9 min; a showpiece 2 h 25 min. Under a Bortle 3 rural sky the solid figure drops to 28 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 3% 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 | 7 min41 subs | 27 min163 subs | 1 h 48 min651 subs |
| Bortle 2Typical dark site | 7 min42 subs | 27 min165 subs | 1 h 50 min658 subs |
| Bortle 3Rural | 7 min42 subs | 28 min168 subs | 1 h 52 min670 subs |
| Bortle 4Rural / suburban transition | 7 min44 subs | 29 min176 subs | 1 h 57 min701 subs |
| Bortle 5Suburban | 8 min47 subs | 31 min188 subs | 2 h 05 min750 subs |
| Bortle 6Bright suburban | 9 min55 subs | 36 min218 subs | 2 h 25 min869 subs |
| Bortle 7Suburban / urban transition | 11 min69 subs | 46 min275 subs | 3 h 03 min1,097 subs |
| Bortle 8City | 15 min91 subs | 1 h363 subs | 4 h 02 min1,451 subs |
| Bortle 9Inner city | 23 min138 subs | 1 h 32 min552 subs | 6 h 07 min2,205 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 47 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 Little Dumbbell is 2.7′ × 1.8′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 3% 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 | 28 min168 subs | 31 min188 subs | 46 min275 subs |
| 20 s | 22 min67 subs | 26 min77 subs | 40 min121 subs |
| 30 s | 20 min41 subs | 24 min48 subs | 38 min77 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 36 min37 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 22 min135 subs | 33 min199 subs | 1 h 20 min483 subs |
| dual-band (LP filter) | 28 min168 subs | 31 min188 subs | 46 min275 subs |
About the Little Dumbbell
A small, bright-per-pixel planetary in Perseus. Dual-band makes the two lobes and the faint wings much easier.
M76, NGC 650 · Planetary nebula in Perseus · magnitude 10.1 · 2.7′ × 1.8′ · best in Sep, Oct, Nov. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
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 Little Dumbbell 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
- Little Dumbbell with the ZWO Seestar S50: 33 min from Bortle 6
- Little Dumbbell with the ZWO Seestar S30: 37 min from Bortle 6
- Little Dumbbell with the ZWO Seestar S30 Pro: 39 min from Bortle 6
- Little Dumbbell with the DwarfLab DWARF 3: 43 min from Bortle 6
- Little Dumbbell with the DwarfLab DWARF mini: 32 min from Bortle 6
- Little Dumbbell with the DwarfLab Draco: 26 min from Bortle 6
- Little Dumbbell with the DwarfLab DWARF II: 2 h 32 min from Bortle 6
- Little Dumbbell with the Vaonis Vespera II: 45 min from Bortle 6
- Little Dumbbell with the Vaonis Vespera Pro: 1 h 41 min from Bortle 6
- Little Dumbbell with the Vaonis Vespera 3: 43 min from Bortle 6
- Little Dumbbell with the Vaonis Vespera Pro 2: 1 h 36 min from Bortle 6
- Little Dumbbell with the Unistellar eQuinox 2: 40 min from Bortle 6
- Little Dumbbell with the Unistellar Odyssey: 3 h 01 min from Bortle 6
- Little Dumbbell with the Celestron Origin: 12 min from Bortle 6
- Little Dumbbell with the Celestron Origin Mark II: 17 min from Bortle 6
All telescopes for the Little Dumbbell · All targets for the Seestar S50 Pro