How long to image the Witch Head Nebula with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 59 h (14,096 subs of 15 s) for a solid image of the Witch Head Nebula. A quick look takes 15 h; a showpiece 230+ h. Under a Bortle 3 rural sky the solid figure drops to 17 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 1.8× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 3 h 19 min796 subs | 13 h3,184 subs | 53 h12,735 subs |
| Bortle 2Typical dark site | 3 h 40 min880 subs | 15 h3,519 subs | 59 h14,076 subs |
| Bortle 3Rural | 4 h 20 min1,039 subs | 17 h4,153 subs | 69 h16,611 subs |
| Bortle 4Rural / suburban transition | 5 h 56 min1,423 subs | 24 h5,689 subs | 95 h22,755 subs |
| Bortle 5Suburban | 8 h 28 min2,031 subs | 34 h8,123 subs | 140+ h32,492 subs |
| Bortle 6Bright suburban | 15 h3,524 subs | 59 h14,096 subs | 230+ h56,382 subs |
| Bortle 7Suburban / urban transition | 27 h6,369 subs | 110+ h25,476 subs | 420+ h101,904 subs |
| Bortle 8City | 45 h10,787 subs | 180+ h43,146 subs | 720+ h172,582 subs |
| Bortle 9Inner city | 84 h20,208 subs | 340+ h80,830 subs | 1350+ h323,318 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 76 h of run time. That is more than one night: over 11 nights, about 6 h 56 min each. The DWARF 3’s battery is rated at about 5 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 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 Witch Head Nebula is 180′ × 60′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it is 1.8× 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 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 | 17 h4,153 subs | 34 h8,123 subs | 110+ h25,476 subs |
| 30 s | 16 h1,904 subs | 32 h3,890 subs | 100+ h12,566 subs |
| 60 s | 15 h909 subs | 32 h1,902 subs | 100+ h6,240 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 10 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 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 Witch Head 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
- 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 mini: 40 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 3