How long to image the M75 with the Vaonis Vespera Pro
From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 42 min (252 subs of 10 s) for a solid image of the M75. A quick look takes 10 min; a showpiece 2 h 47 min. Under a Bortle 3 rural sky the solid figure drops to 22 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 6% 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 | 5 min31 subs | 20 min121 subs | 1 h 20 min483 subs |
| Bortle 2Typical dark site | 5 min32 subs | 21 min125 subs | 1 h 23 min499 subs |
| Bortle 3Rural | 6 min34 subs | 22 min133 subs | 1 h 28 min529 subs |
| Bortle 4Rural / suburban transition | 6 min38 subs | 25 min151 subs | 1 h 40 min603 subs |
| Bortle 5Suburban | 7 min45 subs | 30 min180 subs | 2 h719 subs |
| Bortle 6Bright suburban | 10 min63 subs | 42 min252 subs | 2 h 47 min1,005 subs |
| Bortle 7Suburban / urban transition | 16 min97 subs | 1 h 05 min388 subs | 4 h 18 min1,549 subs |
| Bortle 8City | 25 min150 subs | 1 h 40 min599 subs | 6 h 39 min2,394 subs |
| Bortle 9Inner city | 44 min263 subs | 2 h 55 min1,049 subs | 12 h4,196 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 54 min of run time. The Vespera Pro’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 PD power bank 20000mAh 30WExtends the 11 h battery; 30 W PD per Vaonis.
- 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 Pro →
How it frames
The M75 is 6′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 6% 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 | 22 min133 subs | 30 min180 subs | 1 h 05 min388 subs |
| 20 s | 20 min59 subs | 27 min83 subs | 1 h 02 min187 subs |
| 30 s | 19 min38 subs | 27 min54 subs | 1 h 01 min123 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 Pro
The square-sensor Vespera with 2 µm pixels. Higher resolution than the II, and correspondingly slower per pixel: expect around double the time for the same per-pixel SNR. Run-out in 2026 and replaced by the Vespera Pro 2.
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.
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 Pro? 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 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
All telescopes for the M75 · All targets for the Vespera Pro