How long to image the Witch Head Nebula with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 40 h (9,704 subs of 15 s) for a solid image of the Witch Head Nebula. A quick look takes 10 h; a showpiece 160+ h. Under a Bortle 3 rural sky the solid figure drops to 14 h. At Bortle 6 the limit is skyglow, so a darker site or a filter helps more than longer subs. In this scope's field it is 2.5× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 2 h 45 min660 subs | 11 h2,640 subs | 44 h10,558 subs |
| Bortle 2Typical dark site | 2 h 59 min715 subs | 12 h2,857 subs | 48 h11,426 subs |
| Bortle 3Rural | 3 h 24 min817 subs | 14 h3,267 subs | 54 h13,068 subs |
| Bortle 4Rural / suburban transition | 4 h 26 min1,066 subs | 18 h4,262 subs | 71 h17,045 subs |
| Bortle 5Suburban | 6 h 05 min1,460 subs | 24 h5,837 subs | 97 h23,348 subs |
| Bortle 6Bright suburban | 10 h2,426 subs | 40 h9,704 subs | 160+ h38,814 subs |
| Bortle 7Suburban / urban transition | 18 h4,268 subs | 71 h17,071 subs | 280+ h68,284 subs |
| Bortle 8City | 30 h7,128 subs | 120+ h28,510 subs | 480+ h114,039 subs |
| Bortle 9Inner city | 55 h13,227 subs | 220+ h52,906 subs | 880+ h211,622 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 53 h of run time. That is more than one night: over 8 nights, about 6 h 34 min each. The DWARF mini’s battery is rated at about 3 h 30 min, less near freezing, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a December night.)
- 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.
- 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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How it frames
The Witch Head Nebula is 180′ × 60′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it is 2.5× wider than the frame. A mosaic, or choosing the part you want and letting the rest go, is how it gets shot on this scope.
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 | 14 h3,267 subs | 24 h5,837 subs | 71 h17,071 subs |
| 30 s | 11 h1,345 subs | 22 h2,630 subs | 69 h8,247 subs |
| 60 s | 10 h600 subs | 21 h1,243 subs | 68 h4,051 subs |
| 90 s | 9 h 36 min384 subs | 20 h813 subs | 67 h2,685 subs |
Leave the dual-band filter out for the Witch Head Nebula. It is a reflection nebula, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 12 times slower.
About the Witch Head Nebula
A very faint blue reflection nebula lit by Rigel. A dark-sky, all-night, broadband project; it is one of the hardest objects on this list.
IC 2118 · Reflection nebula in Eridanus · magnitude 13.0 · 180′ × 60′ · best in Nov, Dec, Jan. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.
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 Witch Head 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
- Witch Head Nebula with the ZWO Seestar S50: 41 h from Bortle 6
- Witch Head Nebula with the ZWO Seestar S50 Pro: 44 h from Bortle 6
- Witch Head Nebula with the ZWO Seestar S30: 43 h from Bortle 6
- Witch Head Nebula with the ZWO Seestar S30 Pro: 47 h from Bortle 6
- Witch Head Nebula with the DwarfLab DWARF 3: 59 h from Bortle 6
- Witch Head Nebula with the DwarfLab Draco: 33 h from Bortle 6
- Witch Head Nebula with the DwarfLab DWARF II: 140+ h from Bortle 6
- Witch Head Nebula with the Vaonis Vespera II: 41 h from Bortle 6
- Witch Head Nebula with the Vaonis Vespera Pro: 91 h from Bortle 6
- Witch Head Nebula with the Vaonis Vespera 3: 39 h from Bortle 6
- Witch Head Nebula with the Vaonis Vespera Pro 2: 87 h from Bortle 6
- Witch Head Nebula with the Unistellar eQuinox 2: 38 h from Bortle 6
- Witch Head Nebula with the Unistellar Odyssey: 180+ h from Bortle 6
- Witch Head Nebula with the Celestron Origin: 11 h from Bortle 6
- Witch Head Nebula with the Celestron Origin Mark II: 15 h from Bortle 6
All telescopes for the Witch Head Nebula · All targets for the DWARF mini