How long to image the Thor's Helmet with the DwarfLab Draco
From a Bortle 6 suburban sky, the DwarfLab Draco needs about 4 h 58 min (596 subs of 30 s with the built-in dual-narrowband (Hα + OIII) filter) for a solid image of the Thor's Helmet. A quick look takes 1 h 14 min; a showpiece 20 h. Under a Bortle 3 rural sky the solid figure drops to 3 h 16 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 11% 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 | 47 min94 subs | 3 h 06 min373 subs | 12 h1,492 subs |
| Bortle 2Typical dark site | 47 min95 subs | 3 h 10 min380 subs | 13 h1,519 subs |
| Bortle 3Rural | 49 min99 subs | 3 h 16 min393 subs | 13 h1,571 subs |
| Bortle 4Rural / suburban transition | 53 min106 subs | 3 h 32 min424 subs | 14 h1,696 subs |
| Bortle 5Suburban | 59 min119 subs | 3 h 57 min474 subs | 16 h1,895 subs |
| Bortle 6Bright suburban | 1 h 14 min149 subs | 4 h 58 min596 subs | 20 h2,383 subs |
| Bortle 7Suburban / urban transition | 1 h 43 min207 subs | 6 h 54 min828 subs | 28 h3,312 subs |
| Bortle 8City | 2 h 29 min298 subs | 9 h 54 min1,189 subs | 40 h4,755 subs |
| Bortle 9Inner city | 4 h 05 min490 subs | 16 h1,958 subs | 65 h7,832 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 6 h 27 min of run time. The Draco’s battery is rated at about 5 h, less near freezing, so the session needs an external power bank. (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 20000mAhRated 5 h on its 10,000 mAh battery. DwarfLab has not published the charging input, so check PD support before relying on it mid-session.
- 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 Draco →
How it frames
The Thor's Helmet is 8′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 11% of the frame’s short side.
Longer subs
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 30 s | 3 h 16 min393 subs | 3 h 57 min474 subs | 6 h 54 min828 subs |
| 60 s | 2 h 19 min140 subs | 3 h180 subs | 5 h 57 min357 subs |
| 120 s | 1 h 51 min56 subs | 2 h 31 min76 subs | 5 h 28 min165 subs |
| 300 s | 2 h 30 min30 subs | 2 h 30 min30 subs | 5 h 11 min63 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 2 h 58 min356 subs | 5 h 10 min621 subs | 15 h1,778 subs |
| dual-narrowband (Hα + OIII) | 3 h 16 min393 subs | 3 h 57 min474 subs | 6 h 54 min828 subs |
About the Thor's Helmet
A Wolf-Rayet bubble with wings, strong in OIII. Small and faint; dual-band is essential and a bigger scope helps.
NGC 2359 · Emission nebula in Canis Major · magnitude 11.5 · 8′ · 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 Draco
DwarfLab’s big scope: 90 mm of folded f/3.8 optics, the most aperture of any Seestar or DWARF, a narrow 13 nm dual-band filter and 300 s subs with built-in guiding. A small-target scope; big nebulae need its mosaic mode.
Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Built-in Hα + OIII dual-narrowband filter, 13 nm per line; the SHO Edition adds an SII option.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 30 s and 300 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 Thor's Helmet from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Thor's Helmet with the ZWO Seestar S50: 6 h 17 min from Bortle 6
- Thor's Helmet with the ZWO Seestar S50 Pro: 7 h 04 min from Bortle 6
- Thor's Helmet with the ZWO Seestar S30: 7 h 24 min from Bortle 6
- Thor's Helmet with the ZWO Seestar S30 Pro: 7 h 38 min from Bortle 6
- Thor's Helmet with the DwarfLab DWARF 3: 7 h 41 min from Bortle 6
- Thor's Helmet with the DwarfLab DWARF mini: 6 h 11 min from Bortle 6
- Thor's Helmet with the DwarfLab DWARF II: 36 h from Bortle 6
- Thor's Helmet with the Vaonis Vespera II: 10 h from Bortle 6
- Thor's Helmet with the Vaonis Vespera Pro: 23 h from Bortle 6
- Thor's Helmet with the Vaonis Vespera 3: 9 h 53 min from Bortle 6
- Thor's Helmet with the Vaonis Vespera Pro 2: 22 h from Bortle 6
- Thor's Helmet with the Unistellar eQuinox 2: 9 h 31 min from Bortle 6
- Thor's Helmet with the Unistellar Odyssey: 44 h from Bortle 6
- Thor's Helmet with the Celestron Origin: 2 h 44 min from Bortle 6
- Thor's Helmet with the Celestron Origin Mark II: 3 h 44 min from Bortle 6
All telescopes for the Thor's Helmet · All targets for the Draco