How long to image the Thor's Helmet with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 7 h 38 min (2,749 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 55 min; a showpiece 31 h. Under a Bortle 3 rural sky the solid figure drops to 5 h 20 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 6% 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 17 min460 subs | 5 h 06 min1,837 subs | 20 h7,345 subs |
| Bortle 2Typical dark site | 1 h 18 min467 subs | 5 h 11 min1,865 subs | 21 h7,457 subs |
| Bortle 3Rural | 1 h 20 min480 subs | 5 h 20 min1,918 subs | 21 h7,669 subs |
| Bortle 4Rural / suburban transition | 1 h 25 min512 subs | 5 h 41 min2,046 subs | 23 h8,182 subs |
| Bortle 5Suburban | 1 h 34 min563 subs | 6 h 15 min2,249 subs | 25 h8,996 subs |
| Bortle 6Bright suburban | 1 h 55 min688 subs | 7 h 38 min2,749 subs | 31 h10,994 subs |
| Bortle 7Suburban / urban transition | 2 h 34 min925 subs | 10 h3,700 subs | 41 h14,799 subs |
| Bortle 8City | 3 h 36 min1,295 subs | 14 h5,177 subs | 58 h20,708 subs |
| Bortle 9Inner city | 5 h 47 min2,082 subs | 23 h8,328 subs | 93 h33,309 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 9 h 55 min of run time. That is more than one night: over 2 nights, about 4 h 58 min each. The Seestar S30 Pro’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 January night.)
- USB-C power bank 10000mAh 5V 3A5 V 3 A input and it runs while charging.
- Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
- 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 Pro →
How it frames
The Thor's Helmet is 8′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 6% 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 20 min1,918 subs | 6 h 15 min2,249 subs | 10 h3,700 subs |
| 20 s | 3 h 41 min664 subs | 4 h 37 min830 subs | 8 h 38 min1,555 subs |
| 30 s | 3 h 08 min377 subs | 4 h 04 min488 subs | 8 h 06 min972 subs |
| 60 s | 2 h 36 min156 subs | 3 h 31 min212 subs | 7 h 33 min453 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 4 h 28 min1,609 subs | 7 h 29 min2,693 subs | 21 h7,432 subs |
| dual-band (LP filter) | 5 h 20 min1,918 subs | 6 h 15 min2,249 subs | 10 h3,700 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 Pro
The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.
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 on the telephoto camera.
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 Pro? 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 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 Pro