How long to image the Little Dumbbell with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 37 min (221 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 27 min. Under a Bortle 3 rural sky the solid figure drops to 29 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is small in the frame, about 41 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 7 min43 subs | 28 min170 subs | 1 h 53 min680 subs |
| Bortle 2Typical dark site | 7 min43 subs | 29 min172 subs | 1 h 54 min686 subs |
| Bortle 3Rural | 7 min44 subs | 29 min175 subs | 1 h 56 min698 subs |
| Bortle 4Rural / suburban transition | 8 min46 subs | 30 min182 subs | 2 h 01 min727 subs |
| Bortle 5Suburban | 8 min49 subs | 32 min193 subs | 2 h 09 min772 subs |
| Bortle 6Bright suburban | 9 min56 subs | 37 min221 subs | 2 h 27 min882 subs |
| Bortle 7Suburban / urban transition | 11 min69 subs | 46 min274 subs | 3 h 02 min1,093 subs |
| Bortle 8City | 15 min89 subs | 59 min355 subs | 3 h 57 min1,420 subs |
| Bortle 9Inner city | 22 min133 subs | 1 h 28 min530 subs | 5 h 53 min2,117 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 48 min of run time. The Seestar S30’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 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
- Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and 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 S30 →
How it frames
The Little Dumbbell is 2.7′ × 1.8′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it is small in the frame, about 41 pixels across. It is worth doing, but the result is a crop rather than a full frame; a longer focal length would resolve more of it.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 29 min175 subs | 32 min193 subs | 46 min274 subs |
| 20 s | 22 min67 subs | 25 min76 subs | 39 min116 subs |
| 30 s | 20 min40 subs | 23 min46 subs | 36 min73 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 34 min35 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 22 min134 subs | 32 min194 subs | 1 h 16 min456 subs |
| dual-band (LP filter) | 29 min175 subs | 32 min193 subs | 46 min274 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 S30
Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters.
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 S30? 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 S50 Pro: 36 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 S30