How long to image the Crescent Nebula with the DwarfLab DWARF II
From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 16 h (3,817 subs of 15 s) for a solid image of the Crescent Nebula. A quick look takes 3 h 59 min; a showpiece 64 h. Under a Bortle 3 rural sky the solid figure drops to 7 h 44 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 17% 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 | 1 h 44 min417 subs | 6 h 56 min1,665 subs | 28 h6,660 subs |
| Bortle 2Typical dark site | 1 h 48 min433 subs | 7 h 13 min1,731 subs | 29 h6,924 subs |
| Bortle 3Rural | 1 h 56 min464 subs | 7 h 44 min1,856 subs | 31 h7,424 subs |
| Bortle 4Rural / suburban transition | 2 h 15 min540 subs | 9 h2,159 subs | 36 h8,635 subs |
| Bortle 5Suburban | 2 h 45 min660 subs | 11 h2,639 subs | 44 h10,555 subs |
| Bortle 6Bright suburban | 3 h 59 min955 subs | 16 h3,817 subs | 64 h15,266 subs |
| Bortle 7Suburban / urban transition | 6 h 19 min1,516 subs | 25 h6,061 subs | 100+ h24,242 subs |
| Bortle 8City | 9 h 57 min2,387 subs | 40 h9,545 subs | 160+ h38,178 subs |
| Bortle 9Inner city | 18 h4,244 subs | 71 h16,975 subs | 280+ h67,899 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 21 h of run time. That is more than one night: over 3 nights, about 6 h 53 min each. The DWARF II’s battery is rated at about 3 h, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C PD power bank 10000mAh 18W18 W PD input; runs while charging.
- 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 II →
How it frames
The Crescent Nebula is 18′ × 12′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 17% of the frame’s short side.
Filters
The Crescent Nebula is an emission target, where a dual-band filter would normally cut the time several-fold from a lit sky, but the DWARF II has no dual-band option: Two built-in filters, VIS and Astro (IR-pass); no dual-band. The optional UHC filter is no longer sold. The figures above are for the Astro position, and a darker sky is the lever that remains.
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 II
The original pocket scope. 24 mm aperture and tiny 1.45 µm pixels mean it is slow per pixel, so bin or downsample and be patient.
15 s is the hard maximum in any mode; DwarfLab recommends EQ mode at 15 s. Two built-in filters, VIS and Astro (IR-pass); no dual-band. The optional UHC filter is no longer sold.
The DWARF II uses fixed 15 s subs, so the only levers you have are the sky you shoot from, the filter, and total time.
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 II? 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 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 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 II