How long to image the Thor's Helmet with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 6 h 11 min (1,486 subs of 15 s with the built-in dual-band filter) for a solid image of the Thor's Helmet. A quick look takes 1 h 33 min; a showpiece 25 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 10 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 | 59 min238 subs | 3 h 58 min952 subs | 16 h3,805 subs |
| Bortle 2Typical dark site | 1 h242 subs | 4 h 02 min968 subs | 16 h3,871 subs |
| Bortle 3Rural | 1 h 02 min250 subs | 4 h 10 min999 subs | 17 h3,995 subs |
| Bortle 4Rural / suburban transition | 1 h 07 min269 subs | 4 h 28 min1,074 subs | 18 h4,296 subs |
| Bortle 5Suburban | 1 h 15 min299 subs | 4 h 58 min1,194 subs | 20 h4,773 subs |
| Bortle 6Bright suburban | 1 h 33 min372 subs | 6 h 11 min1,486 subs | 25 h5,943 subs |
| Bortle 7Suburban / urban transition | 2 h 08 min511 subs | 8 h 31 min2,044 subs | 34 h8,173 subs |
| Bortle 8City | 3 h 02 min728 subs | 12 h2,909 subs | 48 h11,635 subs |
| Bortle 9Inner city | 4 h 57 min1,189 subs | 20 h4,755 subs | 79 h19,018 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 8 h 03 min of run time. That is more than one night: over 2 nights, about 4 h 01 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 January 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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Everything that fits the DWARF mini →
How it frames
The Thor's Helmet is 8′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 11% of the frame’s short side.
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 | 4 h 10 min999 subs | 4 h 58 min1,194 subs | 8 h 31 min2,044 subs |
| 30 s | 2 h 57 min354 subs | 3 h 45 min451 subs | 7 h 18 min876 subs |
| 60 s | 2 h 20 min141 subs | 3 h 09 min189 subs | 6 h 41 min402 subs |
| 90 s | 2 h 08 min86 subs | 2 h 57 min118 subs | 6 h 29 min260 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 3 h 40 min882 subs | 6 h 19 min1,517 subs | 18 h4,294 subs |
| dual-band | 4 h 10 min999 subs | 4 h 58 min1,194 subs | 8 h 31 min2,044 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 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 Thor's Helmet from a DWARF mini? 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 Draco: 4 h 58 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 DWARF mini