How long to image the Rosette Nebula with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 1 h 46 min (424 subs of 15 s with the built-in dual-band filter) for a solid image of the Rosette Nebula. A quick look takes 26 min; a showpiece 7 h 03 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 06 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 81% 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 | 15 min62 subs | 1 h 02 min248 subs | 4 h 08 min992 subs |
| Bortle 2Typical dark site | 16 min64 subs | 1 h 03 min254 subs | 4 h 13 min1,014 subs |
| Bortle 3Rural | 16 min66 subs | 1 h 06 min264 subs | 4 h 24 min1,055 subs |
| Bortle 4Rural / suburban transition | 18 min73 subs | 1 h 12 min289 subs | 4 h 48 min1,153 subs |
| Bortle 5Suburban | 20 min82 subs | 1 h 22 min328 subs | 5 h 27 min1,310 subs |
| Bortle 6Bright suburban | 26 min106 subs | 1 h 46 min424 subs | 7 h 03 min1,694 subs |
| Bortle 7Suburban / urban transition | 38 min152 subs | 2 h 32 min607 subs | 10 h2,425 subs |
| Bortle 8City | 56 min223 subs | 3 h 42 min890 subs | 15 h3,560 subs |
| Bortle 9Inner city | 1 h 33 min374 subs | 6 h 14 min1,496 subs | 25 h5,982 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 18 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, and 30% off the battery for a January night.)
- 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.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the DWARF 3 →
How it frames
The Rosette Nebula is 80′ × 60′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 81% 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 | 1 h 06 min264 subs | 1 h 22 min328 subs | 2 h 32 min607 subs |
| 30 s | 57 min114 subs | 1 h 13 min146 subs | 2 h 22 min285 subs |
| 60 s | 52 min53 subs | 1 h 08 min68 subs | 2 h 18 min138 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 1 h 06 min265 subs | 1 h 58 min473 subs | 5 h 46 min1,384 subs |
| dual-band | 1 h 06 min264 subs | 1 h 22 min328 subs | 2 h 32 min607 subs |
About the Rosette Nebula
A ring of hydrogen more than a degree across around the cluster NGC 2244. One of the best dual-band targets of winter and forgiving of light pollution.
NGC 2237, NGC 2244, Caldwell 49 · Emission nebula in Monoceros · magnitude 9.0 · 80′ × 60′ · best in Dec, Jan, Feb. 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 Rosette 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
- Rosette Nebula with the ZWO Seestar S50: 1 h 25 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S50 Pro: 1 h 36 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S30: 1 h 39 min from Bortle 6
- Rosette Nebula with the ZWO Seestar S30 Pro: 1 h 43 min from Bortle 6
- Rosette Nebula with the DwarfLab DWARF mini: 1 h 24 min from Bortle 6
- Rosette Nebula with the DwarfLab Draco: 1 h 08 min from Bortle 6
- Rosette Nebula with the DwarfLab DWARF II: 7 h 45 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera II: 2 h 15 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera Pro: 5 h 04 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera 3: 2 h 09 min from Bortle 6
- Rosette Nebula with the Vaonis Vespera Pro 2: 4 h 49 min from Bortle 6
- Rosette Nebula with the Unistellar eQuinox 2: 2 h 04 min from Bortle 6
- Rosette Nebula with the Unistellar Odyssey: 9 h 33 min from Bortle 6
- Rosette Nebula with the Celestron Origin: 36 min from Bortle 6
- Rosette Nebula with the Celestron Origin Mark II: 49 min from Bortle 6
All telescopes for the Rosette Nebula · All targets for the DWARF 3