How long to image the M78 with the ZWO Seestar S50 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 1 h 09 min (412 subs of 10 s) for a solid image of the M78. A quick look takes 17 min; a showpiece 4 h 34 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 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 | 6 min39 subs | 26 min154 subs | 1 h 42 min613 subs |
| Bortle 2Typical dark site | 7 min41 subs | 27 min162 subs | 1 h 47 min645 subs |
| Bortle 3Rural | 7 min45 subs | 29 min177 subs | 1 h 57 min705 subs |
| Bortle 4Rural / suburban transition | 9 min54 subs | 35 min213 subs | 2 h 22 min850 subs |
| Bortle 5Suburban | 11 min68 subs | 45 min271 subs | 3 h1,081 subs |
| Bortle 6Bright suburban | 17 min103 subs | 1 h 09 min412 subs | 4 h 34 min1,646 subs |
| Bortle 7Suburban / urban transition | 28 min171 subs | 1 h 53 min681 subs | 7 h 34 min2,724 subs |
| Bortle 8City | 46 min275 subs | 3 h 03 min1,100 subs | 12 h4,397 subs |
| Bortle 9Inner city | 1 h 23 min498 subs | 5 h 32 min1,992 subs | 22 h7,966 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 29 min of run time. The Seestar S50 Pro’s battery (rated about 9 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 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.
Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.
Everything that fits the Seestar S50 Pro →
How it frames
The M78 is 8′ × 6′ 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 | 29 min177 subs | 45 min271 subs | 1 h 53 min681 subs |
| 20 s | 25 min77 subs | 41 min124 subs | 1 h 50 min329 subs |
| 30 s | 24 min49 subs | 40 min80 subs | 1 h 48 min217 subs |
| 60 s | 30 min30 subs | 38 min39 subs | 1 h 47 min107 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 12 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 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 M78 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
- M78 with the ZWO Seestar S50: 1 h 03 min from Bortle 6
- M78 with the ZWO Seestar S30: 1 h 06 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 S50 Pro