How long to image the Thor's Helmet with the ZWO Seestar S50
From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 6 h 17 min (2,265 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Thor's Helmet. A quick look takes 1 h 34 min; a showpiece 25 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 16 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 19% 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 | 1 h 01 min366 subs | 4 h 04 min1,464 subs | 16 h5,853 subs |
| Bortle 2Typical dark site | 1 h 02 min372 subs | 4 h 08 min1,488 subs | 17 h5,951 subs |
| Bortle 3Rural | 1 h 04 min384 subs | 4 h 16 min1,535 subs | 17 h6,138 subs |
| Bortle 4Rural / suburban transition | 1 h 09 min412 subs | 4 h 35 min1,648 subs | 18 h6,589 subs |
| Bortle 5Suburban | 1 h 16 min457 subs | 5 h 04 min1,826 subs | 20 h7,304 subs |
| Bortle 6Bright suburban | 1 h 34 min567 subs | 6 h 17 min2,265 subs | 25 h9,060 subs |
| Bortle 7Suburban / urban transition | 2 h 09 min776 subs | 8 h 37 min3,102 subs | 34 h12,405 subs |
| Bortle 8City | 3 h 03 min1,100 subs | 12 h4,400 subs | 49 h17,598 subs |
| Bortle 9Inner city | 4 h 59 min1,793 subs | 20 h7,169 subs | 80 h28,673 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 8 h 11 min of run time. That is more than one night: over 2 nights, about 4 h 05 min each. The Seestar S50’s battery is rated at about 6 h, less near freezing, which is cutting it fine; take a power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a January night.)
- USB-C power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
- Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks stray light.
- 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 Seestar S50 →
How it frames
The Thor's Helmet is 8′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 19% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 4 h 16 min1,535 subs | 5 h 04 min1,826 subs | 8 h 37 min3,102 subs |
| 20 s | 3 h540 subs | 3 h 48 min686 subs | 7 h 21 min1,323 subs |
| 30 s | 2 h 34 min309 subs | 3 h 23 min407 subs | 6 h 56 min832 subs |
| 60 s | 2 h 09 min130 subs | 2 h 58 min178 subs | 6 h 30 min391 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 3 h 43 min1,340 subs | 6 h 22 min2,293 subs | 18 h6,458 subs |
| dual-band (LP filter) | 4 h 16 min1,535 subs | 5 h 04 min1,826 subs | 8 h 37 min3,102 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 ZWO Seestar S50
The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 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 Thor's Helmet from a Seestar S50? 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 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 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 Seestar S50