How long to image the M78 with the ZWO Seestar S30
From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 1 h 06 min (395 subs of 10 s) for a solid image of the M78. A quick look takes 16 min; a showpiece 4 h 23 min. Under a Bortle 3 rural sky the solid figure drops to 29 min. At Bortle 6 the limit is skyglow, so a darker site or a filter helps more than longer subs. 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 | 6 min39 subs | 26 min156 subs | 1 h 44 min622 subs |
| Bortle 2Typical dark site | 7 min41 subs | 27 min163 subs | 1 h 49 min652 subs |
| Bortle 3Rural | 7 min45 subs | 29 min177 subs | 1 h 58 min707 subs |
| Bortle 4Rural / suburban transition | 9 min53 subs | 35 min211 subs | 2 h 20 min842 subs |
| Bortle 5Suburban | 11 min66 subs | 44 min264 subs | 2 h 56 min1,055 subs |
| Bortle 6Bright suburban | 16 min99 subs | 1 h 06 min395 subs | 4 h 23 min1,578 subs |
| Bortle 7Suburban / urban transition | 27 min161 subs | 1 h 47 min644 subs | 7 h 09 min2,574 subs |
| Bortle 8City | 43 min258 subs | 2 h 52 min1,031 subs | 11 h4,121 subs |
| Bortle 9Inner city | 1 h 17 min464 subs | 5 h 09 min1,856 subs | 21 h7,421 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 25 min of run time. The Seestar S30’s battery (rated about 6 h) should cover it; 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 December 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 M78 is 8′ × 6′ 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 | 29 min177 subs | 44 min264 subs | 1 h 47 min644 subs |
| 20 s | 25 min74 subs | 39 min118 subs | 1 h 42 min308 subs |
| 30 s | 23 min46 subs | 37 min75 subs | 1 h 41 min202 subs |
| 60 s | 30 min30 subs | 36 min36 subs | 1 h 39 min100 subs |
Leave the dual-band filter out for the M78. It is a reflection nebula, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 13 times slower.
About the M78
The brightest reflection nebula in the sky, blue dust lit by young stars in Orion's belt. No filter; it is starlight.
NGC 2068 · Reflection nebula in Orion · magnitude 8.3 · 8′ × 6′ · best in Nov, Dec, Jan. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.
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 M78 from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M78 with the ZWO Seestar S50: 1 h 03 min from Bortle 6
- M78 with the ZWO Seestar S50 Pro: 1 h 09 min from Bortle 6
- M78 with the ZWO Seestar S30 Pro: 1 h 13 min from Bortle 6
- M78 with the DwarfLab DWARF 3: 1 h 31 min from Bortle 6
- M78 with the DwarfLab DWARF mini: 1 h 02 min from Bortle 6
- M78 with the DwarfLab Draco: 52 min from Bortle 6
- M78 with the DwarfLab DWARF II: 3 h 32 min from Bortle 6
- M78 with the Vaonis Vespera II: 1 h 03 min from Bortle 6
- M78 with the Vaonis Vespera Pro: 2 h 20 min from Bortle 6
- M78 with the Vaonis Vespera 3: 1 h from Bortle 6
- M78 with the Vaonis Vespera Pro 2: 2 h 13 min from Bortle 6
- M78 with the Unistellar eQuinox 2: 56 min from Bortle 6
- M78 with the Unistellar Odyssey: 4 h 16 min from Bortle 6
- M78 with the Celestron Origin: 17 min from Bortle 6
- M78 with the Celestron Origin Mark II: 23 min from Bortle 6
All telescopes for the M78 · All targets for the Seestar S30