How long to image the Little Dumbbell with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 43 min (171 subs of 15 s with the built-in dual-band filter) for a solid image of the Little Dumbbell. A quick look takes 11 min; a showpiece 2 h 50 min. Under a Bortle 3 rural sky the solid figure drops to 31 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 59 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 7 min30 subs | 30 min119 subs | 1 h 58 min474 subs |
| Bortle 2Typical dark site | 7 min30 subs | 30 min120 subs | 2 h480 subs |
| Bortle 3Rural | 8 min31 subs | 31 min123 subs | 2 h 03 min492 subs |
| Bortle 4Rural / suburban transition | 8 min33 subs | 33 min131 subs | 2 h 10 min521 subs |
| Bortle 5Suburban | 9 min36 subs | 35 min142 subs | 2 h 22 min568 subs |
| Bortle 6Bright suburban | 11 min43 subs | 43 min171 subs | 2 h 50 min682 subs |
| Bortle 7Suburban / urban transition | 14 min57 subs | 56 min225 subs | 3 h 44 min898 subs |
| Bortle 8City | 19 min78 subs | 1 h 17 min309 subs | 5 h 09 min1,235 subs |
| Bortle 9Inner city | 31 min123 subs | 2 h 02 min489 subs | 8 h 08 min1,954 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 55 min of run time. The DWARF 3’s battery (rated about 5 h 30 min) 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 18W18 W PD input and it runs while charging; needs a C-to-C cable for PD.
- 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 DWARF 3 →
How it frames
The Little Dumbbell is 2.7′ × 1.8′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it is small in the frame, about 59 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
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 31 min123 subs | 35 min142 subs | 56 min225 subs |
| 30 s | 28 min56 subs | 33 min66 subs | 53 min107 subs |
| 60 s | 30 min30 subs | 31 min32 subs | 52 min53 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 27 min110 subs | 43 min172 subs | 1 h 50 min442 subs |
| dual-band | 31 min123 subs | 35 min142 subs | 56 min225 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 DwarfLab DWARF 3
Small pixels on a 35 mm f/4.3 lens give a sharper image than its aperture suggests, and EQ mode with 60 s subs makes it the read-noise winner in dark skies.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Three built-in filters: VIS, Astro (430 to 690 nm) and dual-band Hα 656 nm / OIII 501 nm.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 15 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 DWARF 3? 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: 37 min from Bortle 6
- Little Dumbbell with the ZWO Seestar S30 Pro: 39 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 DWARF 3