How long to image the Eskimo Nebula with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 14 min (57 subs of 15 s with the built-in dual-band filter) for a solid image of the Eskimo Nebula. A quick look takes 4 min; a showpiece 57 min. Under a Bortle 3 rural sky the solid figure drops to 11 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 17 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 3 min12 subs | 11 min45 subs | 45 min179 subs |
| Bortle 2Typical dark site | 3 min12 subs | 11 min45 subs | 45 min180 subs |
| Bortle 3Rural | 3 min12 subs | 11 min46 subs | 46 min183 subs |
| Bortle 4Rural / suburban transition | 3 min12 subs | 12 min48 subs | 47 min190 subs |
| Bortle 5Suburban | 3 min13 subs | 13 min51 subs | 50 min201 subs |
| Bortle 6Bright suburban | 4 min15 subs | 14 min57 subs | 57 min227 subs |
| Bortle 7Suburban / urban transition | 4 min18 subs | 17 min69 subs | 1 h 09 min276 subs |
| Bortle 8City | 6 min23 subs | 22 min89 subs | 1 h 28 min353 subs |
| Bortle 9Inner city | 8 min33 subs | 32 min130 subs | 2 h 09 min518 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 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 Eskimo Nebula is 0.8′ × 0.7′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it is small in the frame, about 17 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 | 11 min46 subs | 13 min51 subs | 17 min69 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 17 min34 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 30 min30 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 9 min38 subs | 13 min52 subs | 28 min114 subs |
| dual-band | 11 min46 subs | 13 min51 subs | 17 min69 subs |
About the Eskimo Nebula
A small, bright double-shell planetary in Gemini. Tiny in a smart scope but intense; a few minutes show the disc.
NGC 2392, Caldwell 39, Clown Face · Planetary nebula in Gemini · magnitude 9.2 · 0.8′ × 0.7′ · best in Dec, Jan, Feb. 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 Eskimo 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
- Eskimo Nebula with the ZWO Seestar S50: 10 min from Bortle 6
- Eskimo Nebula with the ZWO Seestar S50 Pro: 11 min from Bortle 6
- Eskimo Nebula with the ZWO Seestar S30: 11 min from Bortle 6
- Eskimo Nebula with the ZWO Seestar S30 Pro: 12 min from Bortle 6
- Eskimo Nebula with the DwarfLab DWARF mini: 10 min from Bortle 6
- Eskimo Nebula with the DwarfLab Draco: 15 min from Bortle 6
- Eskimo Nebula with the DwarfLab DWARF II: 40 min from Bortle 6
- Eskimo Nebula with the Vaonis Vespera II: 12 min from Bortle 6
- Eskimo Nebula with the Vaonis Vespera Pro: 27 min from Bortle 6
- Eskimo Nebula with the Vaonis Vespera 3: 12 min from Bortle 6
- Eskimo Nebula with the Vaonis Vespera Pro 2: 26 min from Bortle 6
- Eskimo Nebula with the Unistellar eQuinox 2: 10 min from Bortle 6
- Eskimo Nebula with the Unistellar Odyssey: 46 min from Bortle 6
- Eskimo Nebula with the Celestron Origin: 5 min from Bortle 6
- Eskimo Nebula with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the Eskimo Nebula · All targets for the DWARF 3