How long to image the Witch Head Nebula with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 180+ h (158,877 subs of 4 s) for a solid image of the Witch Head Nebula. A quick look takes 44 h; a showpiece 710+ h. Under a Bortle 3 rural sky the solid figure drops to 120+ h. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is 5.3× wider than the frame.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 27 h24,702 subs | 110+ h98,806 subs | 440+ h395,221 subs |
| Bortle 2Typical dark site | 28 h25,163 subs | 110+ h100,651 subs | 450+ h402,601 subs |
| Bortle 3Rural | 29 h26,036 subs | 120+ h104,141 subs | 460+ h416,561 subs |
| Bortle 4Rural / suburban transition | 31 h28,149 subs | 130+ h112,596 subs | 500+ h450,382 subs |
| Bortle 5Suburban | 35 h31,500 subs | 140+ h125,997 subs | 560+ h503,986 subs |
| Bortle 6Bright suburban | 44 h39,720 subs | 180+ h158,877 subs | 710+ h635,505 subs |
| Bortle 7Suburban / urban transition | 62 h55,382 subs | 250+ h221,527 subs | 980+ h886,108 subs |
| Bortle 8City | 89 h79,701 subs | 350+ h318,801 subs | 1420+ h1,275,204 subs |
| Bortle 9Inner city | 150+ h131,565 subs | 580+ h526,258 subs | 2340+ h2,105,031 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 230+ h of run time. That is more than one night: over 33 nights, about 6 h 57 min each. The Odyssey’s battery is rated at about 5 h, 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 power bank 20000mAh 5V 2.4AUnistellar says plain 5 V 2.4 A and warns against fast or adaptive chargers.
- 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 Odyssey →
How it frames
The Witch Head Nebula is 180′ × 60′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it is 5.3× 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.
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 Unistellar Odyssey
Unistellar’s compact 85 mm with autofocus and tiny pixels. Sharp, but the fine sampling costs time on faint extended targets. The Odyssey Pro is the same telescope with an eyepiece added, so these figures apply to both.
Fixed 4 s subs in Enhanced Vision; they cannot be changed. No filter option; Unistellar says third-party filters cannot be fitted to the Odyssey.
The Odyssey uses fixed 4 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 Witch Head Nebula from a Odyssey? 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 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 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 Odyssey