How long to image the M55 with the Vaonis Vespera Pro
From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 31 min (184 subs of 10 s) for a solid image of the M55. A quick look takes 8 min; a showpiece 2 h 02 min. Under a Bortle 3 rural sky the solid figure drops to 15 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 20% 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 | 3 min21 subs | 14 min83 subs | 55 min329 subs |
| Bortle 2Typical dark site | 4 min22 subs | 14 min86 subs | 57 min341 subs |
| Bortle 3Rural | 4 min23 subs | 15 min92 subs | 1 h 01 min365 subs |
| Bortle 4Rural / suburban transition | 4 min27 subs | 18 min106 subs | 1 h 10 min422 subs |
| Bortle 5Suburban | 5 min32 subs | 21 min128 subs | 1 h 25 min512 subs |
| Bortle 6Bright suburban | 8 min46 subs | 31 min184 subs | 2 h 02 min734 subs |
| Bortle 7Suburban / urban transition | 12 min73 subs | 48 min290 subs | 3 h 13 min1,157 subs |
| Bortle 8City | 19 min114 subs | 1 h 16 min454 subs | 5 h 02 min1,813 subs |
| Bortle 9Inner city | 33 min201 subs | 2 h 14 min803 subs | 8 h 55 min3,212 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 40 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 M55 is 19′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 20% 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 | 15 min92 subs | 21 min128 subs | 48 min290 subs |
| 20 s | 13 min40 subs | 19 min59 subs | 46 min139 subs |
| 30 s | 15 min30 subs | 19 min38 subs | 46 min92 subs |
About the M55
A large, loose globular that resolves easily but sits low for northern imagers.
NGC 6809 · Globular cluster in Sagittarius · magnitude 6.3 · 19′ · best in Jun, Jul, Aug. 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 M55 from a Vespera Pro? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M55 with the ZWO Seestar S50: 14 min from Bortle 6
- M55 with the ZWO Seestar S50 Pro: 15 min from Bortle 6
- M55 with the ZWO Seestar S30: 14 min from Bortle 6
- M55 with the ZWO Seestar S30 Pro: 16 min from Bortle 6
- M55 with the DwarfLab DWARF 3: 20 min from Bortle 6
- M55 with the DwarfLab DWARF mini: 14 min from Bortle 6
- M55 with the DwarfLab Draco: 15 min from Bortle 6
- M55 with the DwarfLab DWARF II: 46 min from Bortle 6
- M55 with the Vaonis Vespera II: 14 min from Bortle 6
- M55 with the Vaonis Vespera 3: 13 min from Bortle 6
- M55 with the Vaonis Vespera Pro 2: 29 min from Bortle 6
- M55 with the Unistellar eQuinox 2: 12 min from Bortle 6
- M55 with the Unistellar Odyssey: 54 min from Bortle 6
- M55 with the Celestron Origin: 5 min from Bortle 6
- M55 with the Celestron Origin Mark II: 5 min from Bortle 6
All telescopes for the M55 · All targets for the Vespera Pro