How long to image the Thor's Helmet with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 7 h 24 min (2,666 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 51 min; a showpiece 30 h. Under a Bortle 3 rural sky the solid figure drops to 5 h 23 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 | 1 h 18 min466 subs | 5 h 11 min1,864 subs | 21 h7,456 subs |
| Bortle 2Typical dark site | 1 h 19 min473 subs | 5 h 15 min1,889 subs | 21 h7,555 subs |
| Bortle 3Rural | 1 h 21 min484 subs | 5 h 23 min1,936 subs | 22 h7,741 subs |
| Bortle 4Rural / suburban transition | 1 h 25 min513 subs | 5 h 41 min2,049 subs | 23 h8,193 subs |
| Bortle 5Suburban | 1 h 33 min557 subs | 6 h 11 min2,227 subs | 25 h8,908 subs |
| Bortle 6Bright suburban | 1 h 51 min667 subs | 7 h 24 min2,666 subs | 30 h10,663 subs |
| Bortle 7Suburban / urban transition | 2 h 26 min876 subs | 9 h 44 min3,502 subs | 39 h14,008 subs |
| Bortle 8City | 3 h 20 min1,201 subs | 13 h4,801 subs | 53 h19,201 subs |
| Bortle 9Inner city | 5 h 15 min1,893 subs | 21 h7,570 subs | 84 h30,277 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 9 h 38 min of run time. That is more than one night: over 2 nights, about 4 h 49 min each. The Seestar S30’s battery is rated at about 6 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 January night.)
- USB-C power bank 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
- Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and 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 S30 →
How it frames
The Thor's Helmet is 8′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 11% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 5 h 23 min1,936 subs | 6 h 11 min2,227 subs | 9 h 44 min3,502 subs |
| 20 s | 3 h 33 min640 subs | 4 h 22 min786 subs | 7 h 54 min1,423 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 |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 4 h 16 min1,537 subs | 6 h 55 min2,489 subs | 18 h6,655 subs |
| dual-band (LP filter) | 5 h 23 min1,936 subs | 6 h 11 min2,227 subs | 9 h 44 min3,502 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 S30
Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters.
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 S30? 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 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 S30