How long to image the M75 with the Unistellar eQuinox 2
From a Bortle 6 suburban sky, the Unistellar eQuinox 2 needs about 16 min (243 subs of 4 s) for a solid image of the M75. A quick look takes 4 min; a showpiece 1 h 05 min. Under a Bortle 3 rural sky the solid figure drops to 10 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 18% 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 | 2 min37 subs | 10 min146 subs | 39 min583 subs |
| Bortle 2Typical dark site | 2 min38 subs | 10 min149 subs | 40 min595 subs |
| Bortle 3Rural | 3 min39 subs | 10 min155 subs | 41 min617 subs |
| Bortle 4Rural / suburban transition | 3 min42 subs | 11 min168 subs | 45 min671 subs |
| Bortle 5Suburban | 3 min48 subs | 13 min190 subs | 50 min758 subs |
| Bortle 6Bright suburban | 4 min61 subs | 16 min243 subs | 1 h 05 min969 subs |
| Bortle 7Suburban / urban transition | 6 min86 subs | 23 min344 subs | 1 h 31 min1,373 subs |
| Bortle 8City | 8 min125 subs | 33 min500 subs | 2 h 13 min1,999 subs |
| Bortle 9Inner city | 14 min209 subs | 56 min834 subs | 3 h 42 min3,334 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 21 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 M75 is 6′ across. The eQuinox 2 frames 0.76° × 0.57° at 1.33″ per pixel, so it fills 18% of the frame’s short side.
About the M75
A remote, tightly packed globular. Small and faint, but its dense core shows up fast.
NGC 6864 · Globular cluster in Sagittarius · magnitude 8.5 · 6′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.
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 M75 from a eQuinox 2? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M75 with the ZWO Seestar S50: 19 min from Bortle 6
- M75 with the ZWO Seestar S50 Pro: 21 min from Bortle 6
- M75 with the ZWO Seestar S30: 20 min from Bortle 6
- M75 with the ZWO Seestar S30 Pro: 22 min from Bortle 6
- M75 with the DwarfLab DWARF 3: 28 min from Bortle 6
- M75 with the DwarfLab DWARF mini: 19 min from Bortle 6
- M75 with the DwarfLab Draco: 16 min from Bortle 6
- M75 with the DwarfLab DWARF II: 1 h 02 min from Bortle 6
- M75 with the Vaonis Vespera II: 19 min from Bortle 6
- M75 with the Vaonis Vespera Pro: 42 min from Bortle 6
- M75 with the Vaonis Vespera 3: 18 min from Bortle 6
- M75 with the Vaonis Vespera Pro 2: 40 min from Bortle 6
- M75 with the Unistellar Odyssey: 1 h 13 min from Bortle 6
- M75 with the Celestron Origin: 5 min from Bortle 6
- M75 with the Celestron Origin Mark II: 7 min from Bortle 6