How long to image the Thor's Helmet with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 7 h 04 min (2,547 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 46 min; a showpiece 28 h. Under a Bortle 3 rural sky the solid figure drops to 4 h 53 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 10% 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 10 min420 subs | 4 h 40 min1,679 subs | 19 h6,716 subs |
| Bortle 2Typical dark site | 1 h 11 min427 subs | 4 h 44 min1,706 subs | 19 h6,823 subs |
| Bortle 3Rural | 1 h 13 min439 subs | 4 h 53 min1,756 subs | 20 h7,024 subs |
| Bortle 4Rural / suburban transition | 1 h 18 min470 subs | 5 h 13 min1,879 subs | 21 h7,513 subs |
| Bortle 5Suburban | 1 h 26 min518 subs | 5 h 45 min2,072 subs | 23 h8,286 subs |
| Bortle 6Bright suburban | 1 h 46 min637 subs | 7 h 04 min2,547 subs | 28 h10,185 subs |
| Bortle 7Suburban / urban transition | 2 h 24 min863 subs | 9 h 35 min3,451 subs | 38 h13,803 subs |
| Bortle 8City | 3 h 22 min1,214 subs | 13 h4,855 subs | 54 h19,420 subs |
| Bortle 9Inner city | 5 h 27 min1,963 subs | 22 h7,850 subs | 87 h31,399 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 9 h 12 min of run time. That is more than one night: over 2 nights, about 4 h 36 min each. The Seestar S50 Pro’s battery (rated about 9 h) should cover each night; a power bank still keeps the phone running the app alive. (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 20000mAh 30WAccepts 12 V 3 A PD, so a 30 W bank tops up the 10,000 mAh cell while imaging.
- Seestar S50 Pro dew shieldDew heater is built in; a shield adds margin on damp nights. Check the listing says S50 Pro.
- 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 Pro →
How it frames
The Thor's Helmet is 8′ across. The Seestar S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 10% of the frame’s short side.
Longer subs
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 4 h 53 min1,756 subs | 5 h 45 min2,072 subs | 9 h 35 min3,451 subs |
| 20 s | 3 h 24 min612 subs | 4 h 16 min770 subs | 8 h 06 min1,459 subs |
| 30 s | 2 h 54 min349 subs | 3 h 47 min454 subs | 7 h 37 min914 subs |
| 60 s | 2 h 25 min145 subs | 3 h 17 min198 subs | 7 h 07 min428 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 4 h 09 min1,497 subs | 7 h 01 min2,527 subs | 20 h7,032 subs |
| dual-band (LP filter) | 4 h 53 min1,756 subs | 5 h 45 min2,072 subs | 9 h 35 min3,451 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 Pro
The S50 optics at 260 mm on an 8 MP 1/1.2-inch sensor: a wider, taller field, four times the pixels, and 60 s subs in EQ mode. Per pixel it is a whisker slower than the S50 because of the longer focal length; the long subs make it the better dark-site scope.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. 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 S50 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 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 Pro