How long to image the Crescent Nebula with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 2 h 47 min (667 subs of 15 s with the built-in dual-band filter) for a solid image of the Crescent Nebula. A quick look takes 42 min; a showpiece 11 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 53 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 25% 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 | 27 min108 subs | 1 h 47 min429 subs | 7 h 09 min1,716 subs |
| Bortle 2Typical dark site | 27 min110 subs | 1 h 49 min437 subs | 7 h 16 min1,746 subs |
| Bortle 3Rural | 28 min113 subs | 1 h 53 min451 subs | 7 h 30 min1,801 subs |
| Bortle 4Rural / suburban transition | 30 min121 subs | 2 h 01 min484 subs | 8 h 03 min1,934 subs |
| Bortle 5Suburban | 34 min135 subs | 2 h 14 min537 subs | 8 h 56 min2,146 subs |
| Bortle 6Bright suburban | 42 min167 subs | 2 h 47 min667 subs | 11 h2,665 subs |
| Bortle 7Suburban / urban transition | 57 min229 subs | 3 h 48 min914 subs | 15 h3,654 subs |
| Bortle 8City | 1 h 21 min325 subs | 5 h 24 min1,298 subs | 22 h5,190 subs |
| Bortle 9Inner city | 2 h 12 min530 subs | 8 h 49 min2,117 subs | 35 h8,465 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 3 h 36 min of run time. The DWARF mini’s battery is rated at about 3 h 30 min, so the session needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C PD power bank 10000mAh 20W7,000 mAh inside, about four hours; a PD bank extends the night.
- 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 mini →
How it frames
The Crescent Nebula is 18′ × 12′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 25% of the frame’s short side.
Longer subs
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 1 h 53 min451 subs | 2 h 14 min537 subs | 3 h 48 min914 subs |
| 30 s | 1 h 20 min161 subs | 1 h 42 min204 subs | 3 h 16 min393 subs |
| 60 s | 1 h 04 min65 subs | 1 h 26 min86 subs | 3 h180 subs |
| 90 s | 59 min40 subs | 1 h 20 min54 subs | 2 h 54 min117 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 1 h 39 min396 subs | 2 h 49 min678 subs | 7 h 57 min1,910 subs |
| dual-band | 1 h 53 min451 subs | 2 h 14 min537 subs | 3 h 48 min914 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 mini
DwarfLab’s answer to the Seestar S30: same sensor and focal length, big pixels, dual-band filter built in, and 90 s subs in EQ mode. Sensitivity over megapixels.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Built-in Astro (430 to 690 nm), dark-frame and dual-band Hα / OIII filters; no plain VIS filter on the tele camera.
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 90 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 mini? 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 3: 3 h 27 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 mini