How long to image the Crescent Nebula with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 3 h 27 min (829 subs of 15 s with the built-in dual-band filter) for a solid image of the Crescent Nebula. A quick look takes 52 min; a showpiece 14 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 04 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 18% 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 | 29 min116 subs | 1 h 56 min463 subs | 7 h 43 min1,851 subs |
| Bortle 2Typical dark site | 30 min119 subs | 1 h 58 min474 subs | 7 h 54 min1,896 subs |
| Bortle 3Rural | 31 min124 subs | 2 h 04 min496 subs | 8 h 15 min1,982 subs |
| Bortle 4Rural / suburban transition | 34 min137 subs | 2 h 17 min547 subs | 9 h 07 min2,188 subs |
| Bortle 5Suburban | 39 min158 subs | 2 h 37 min629 subs | 10 h2,515 subs |
| Bortle 6Bright suburban | 52 min208 subs | 3 h 27 min829 subs | 14 h3,316 subs |
| Bortle 7Suburban / urban transition | 1 h 16 min303 subs | 5 h 03 min1,211 subs | 20 h4,844 subs |
| Bortle 8City | 1 h 53 min452 subs | 7 h 31 min1,805 subs | 30 h7,217 subs |
| Bortle 9Inner city | 3 h 12 min768 subs | 13 h3,069 subs | 51 h12,276 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 4 h 29 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 Crescent Nebula is 18′ × 12′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 18% of the frame’s short side.
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 | 2 h 04 min496 subs | 2 h 37 min629 subs | 5 h 03 min1,211 subs |
| 30 s | 1 h 45 min210 subs | 2 h 18 min276 subs | 4 h 43 min567 subs |
| 60 s | 1 h 35 min95 subs | 2 h 08 min129 subs | 4 h 34 min274 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 2 h 08 min514 subs | 3 h 57 min949 subs | 12 h2,852 subs |
| dual-band | 2 h 04 min496 subs | 2 h 37 min629 subs | 5 h 03 min1,211 subs |
About the Crescent Nebula
A shell blown by a Wolf-Rayet star, bright in H-alpha with a faint OIII skin. Small, so the bigger scopes do it justice.
NGC 6888, Caldwell 27 · Emission nebula in Cygnus · magnitude 7.4 · 18′ × 12′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.
Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.
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 Crescent Nebula from a DWARF 3? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Crescent Nebula with the ZWO Seestar S50: 2 h 49 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S50 Pro: 3 h 10 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S30: 3 h 19 min from Bortle 6
- Crescent Nebula with the ZWO Seestar S30 Pro: 3 h 25 min from Bortle 6
- Crescent Nebula with the DwarfLab DWARF mini: 2 h 47 min from Bortle 6
- Crescent Nebula with the DwarfLab Draco: 2 h 14 min from Bortle 6
- Crescent Nebula with the DwarfLab DWARF II: 16 h from Bortle 6
- Crescent Nebula with the Vaonis Vespera II: 4 h 37 min from Bortle 6
- Crescent Nebula with the Vaonis Vespera Pro: 10 h from Bortle 6
- Crescent Nebula with the Vaonis Vespera 3: 4 h 24 min from Bortle 6
- Crescent Nebula with the Vaonis Vespera Pro 2: 9 h 52 min from Bortle 6
- Crescent Nebula with the Unistellar eQuinox 2: 4 h 14 min from Bortle 6
- Crescent Nebula with the Unistellar Odyssey: 20 h from Bortle 6
- Crescent Nebula with the Celestron Origin: 1 h 13 min from Bortle 6
- Crescent Nebula with the Celestron Origin Mark II: 1 h 40 min from Bortle 6
All telescopes for the Crescent Nebula · All targets for the DWARF 3