How long to image the M75 with the Vaonis Vespera II
From a Bortle 6 suburban sky, the Vaonis Vespera II needs about 19 min (114 subs of 10 s) for a solid image of the M75. A quick look takes 5 min; a showpiece 1 h 16 min. Under a Bortle 3 rural sky the solid figure drops to 9 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 7% 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 min13 subs | 9 min52 subs | 34 min206 subs |
| Bortle 2Typical dark site | 2 min14 subs | 9 min54 subs | 36 min214 subs |
| Bortle 3Rural | 2 min15 subs | 9 min57 subs | 38 min228 subs |
| Bortle 4Rural / suburban transition | 3 min17 subs | 11 min66 subs | 44 min263 subs |
| Bortle 5Suburban | 3 min20 subs | 13 min80 subs | 53 min318 subs |
| Bortle 6Bright suburban | 5 min29 subs | 19 min114 subs | 1 h 16 min454 subs |
| Bortle 7Suburban / urban transition | 7 min45 subs | 30 min179 subs | 1 h 59 min713 subs |
| Bortle 8City | 12 min70 subs | 46 min279 subs | 3 h 06 min1,115 subs |
| Bortle 9Inner city | 21 min124 subs | 1 h 22 min493 subs | 5 h 29 min1,972 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 25 min of run time. The Vespera II’s battery (rated about 4 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 PD power bank 20000mAh 30WOnly four hours inside; Vaonis specifies a 30 W PD source. C-to-C cable not included.
- Vaonis Vespera hygrometer sensorTriggers the built-in demister automatically; the correct dew accessory for the II.
- 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 Vespera II →
How it frames
The M75 is 6′ across. The Vespera II frames 2.55° × 1.44° at 2.39″ per pixel, so it fills 7% of the frame’s short side.
Longer subs
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 9 min57 subs | 13 min80 subs | 30 min179 subs |
| 20 s | 10 min30 subs | 12 min38 subs | 29 min87 subs |
| 30 s | 15 min30 subs | 15 min30 subs | 29 min58 subs |
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 Vaonis Vespera II
A 50 mm quadruplet on an 8 MP sensor with Vaonis’s mosaic mode for wide fields. Same optics class as the Seestar S50, four times the pixels.
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only, no EQ mode. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar; the app detects which is fitted.
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 30 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 M75 from a Vespera II? 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 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 eQuinox 2: 16 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