How long to image the Little Dumbbell with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 33 min (196 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 8 min; a showpiece 2 h 10 min. Under a Bortle 3 rural sky the solid figure drops to 25 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 6% 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 | 6 min37 subs | 24 min145 subs | 1 h 36 min579 subs |
| Bortle 2Typical dark site | 6 min37 subs | 24 min147 subs | 1 h 37 min585 subs |
| Bortle 3Rural | 6 min38 subs | 25 min150 subs | 1 h 39 min597 subs |
| Bortle 4Rural / suburban transition | 7 min40 subs | 26 min157 subs | 1 h 44 min626 subs |
| Bortle 5Suburban | 7 min42 subs | 28 min168 subs | 1 h 52 min671 subs |
| Bortle 6Bright suburban | 8 min49 subs | 33 min196 subs | 2 h 10 min781 subs |
| Bortle 7Suburban / urban transition | 10 min62 subs | 41 min248 subs | 2 h 45 min992 subs |
| Bortle 8City | 14 min83 subs | 55 min330 subs | 3 h 40 min1,319 subs |
| Bortle 9Inner city | 21 min126 subs | 1 h 24 min504 subs | 5 h 36 min2,016 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 42 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.)
- 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.
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Everything that fits the Seestar S50 →
How it frames
The Little Dumbbell is 2.7′ × 1.8′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 6% of the frame’s short side.
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 | 25 min150 subs | 28 min168 subs | 41 min248 subs |
| 20 s | 20 min61 subs | 23 min70 subs | 37 min110 subs |
| 30 s | 18 min37 subs | 22 min44 subs | 35 min70 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 33 min34 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 20 min122 subs | 30 min182 subs | 1 h 14 min444 subs |
| dual-band (LP filter) | 25 min150 subs | 28 min168 subs | 41 min248 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
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 Little Dumbbell from a Seestar S50? 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 Pro: 36 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