How long to image the M108 with the Unistellar eQuinox 2
From a Bortle 6 suburban sky, the Unistellar eQuinox 2 needs about 1 h 18 min (1,163 subs of 4 s) for a solid image of the M108. A quick look takes 19 min; a showpiece 5 h 10 min. Under a Bortle 3 rural sky the solid figure drops to 46 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 25% 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 | 11 min160 subs | 42 min637 subs | 2 h 50 min2,548 subs |
| Bortle 2Typical dark site | 11 min164 subs | 44 min654 subs | 2 h 54 min2,613 subs |
| Bortle 3Rural | 11 min171 subs | 46 min684 subs | 3 h 02 min2,735 subs |
| Bortle 4Rural / suburban transition | 13 min190 subs | 51 min758 subs | 3 h 22 min3,031 subs |
| Bortle 5Suburban | 15 min219 subs | 58 min875 subs | 3 h 53 min3,500 subs |
| Bortle 6Bright suburban | 19 min291 subs | 1 h 18 min1,163 subs | 5 h 10 min4,652 subs |
| Bortle 7Suburban / urban transition | 29 min428 subs | 1 h 54 min1,712 subs | 7 h 36 min6,846 subs |
| Bortle 8City | 43 min641 subs | 2 h 51 min2,564 subs | 11 h10,254 subs |
| Bortle 9Inner city | 1 h 13 min1,095 subs | 4 h 52 min4,380 subs | 19 h17,520 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 41 min of run time. The eQuinox 2’s battery (rated about 11 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.)
- USB-C power bank 20000mAh 5V 2AUnistellar asks for a 5 V 2 A output; PD is not needed.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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Everything that fits the eQuinox 2 →
How it frames
The M108 is 8.7′ × 2.2′ across. The eQuinox 2 frames 0.76° × 0.57° at 1.33″ per pixel, so it fills 25% of the frame’s short side.
About the M108
An edge-on spiral with a mottled, dusty disc, a degree from the Owl Nebula. Frame both together.
NGC 3556 · Galaxy in Ursa Major · magnitude 10.0 · 8.7′ × 2.2′ · best in Feb, Mar, Apr. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.
Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.
About the Unistellar eQuinox 2
A 114 mm Newtonian with five times the light grasp of a 50 mm refractor. Fixed 4 s subs put it in read-noise territory under dark skies, but the aperture carries it. The published field is 45.6′ × 34.2′, a crop of the sensor.
Fixed 4 s subs in Enhanced Vision; they cannot be changed. No built-in filter. Unistellar sells only a solar filter and says a third-party filter is at your own risk and voids the warranty.
The eQuinox 2 uses fixed 4 s subs, so the only levers you have are the sky you shoot from, the filter, and total time.
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 M108 from a eQuinox 2? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M108 with the ZWO Seestar S50: 1 h 26 min from Bortle 6
- M108 with the ZWO Seestar S50 Pro: 1 h 34 min from Bortle 6
- M108 with the ZWO Seestar S30: 1 h 30 min from Bortle 6
- M108 with the ZWO Seestar S30 Pro: 1 h 40 min from Bortle 6
- M108 with the DwarfLab DWARF 3: 2 h 06 min from Bortle 6
- M108 with the DwarfLab DWARF mini: 1 h 26 min from Bortle 6
- M108 with the DwarfLab Draco: 1 h 11 min from Bortle 6
- M108 with the DwarfLab DWARF II: 4 h 54 min from Bortle 6
- M108 with the Vaonis Vespera II: 1 h 26 min from Bortle 6
- M108 with the Vaonis Vespera Pro: 3 h 13 min from Bortle 6
- M108 with the Vaonis Vespera 3: 1 h 22 min from Bortle 6
- M108 with the Vaonis Vespera Pro 2: 3 h 04 min from Bortle 6
- M108 with the Unistellar Odyssey: 5 h 57 min from Bortle 6
- M108 with the Celestron Origin: 23 min from Bortle 6
- M108 with the Celestron Origin Mark II: 31 min from Bortle 6