How long to image the Abell 39 with the Vaonis Vespera Pro 2
From a Bortle 6 suburban sky, the Vaonis Vespera Pro 2 needs about 79 h (28,348 subs of 10 s) for a solid image of the Abell 39. A quick look takes 20 h; a showpiece 310+ h. Under a Bortle 3 rural sky the solid figure drops to 30 h. 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 3% 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 | 6 h 23 min2,296 subs | 26 h9,183 subs | 100+ h36,730 subs |
| Bortle 2Typical dark site | 6 h 47 min2,443 subs | 27 h9,771 subs | 110+ h39,084 subs |
| Bortle 3Rural | 7 h 34 min2,722 subs | 30 h10,885 subs | 120+ h43,538 subs |
| Bortle 4Rural / suburban transition | 9 h 26 min3,396 subs | 38 h13,583 subs | 150+ h54,329 subs |
| Bortle 5Suburban | 12 h4,465 subs | 50 h17,858 subs | 200+ h71,430 subs |
| Bortle 6Bright suburban | 20 h7,087 subs | 79 h28,348 subs | 310+ h113,390 subs |
| Bortle 7Suburban / urban transition | 34 h12,084 subs | 130+ h48,336 subs | 540+ h193,344 subs |
| Bortle 8City | 55 h19,843 subs | 220+ h79,371 subs | 880+ h317,482 subs |
| Bortle 9Inner city | 100+ h36,390 subs | 400+ h145,558 subs | 1620+ h582,232 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 100+ h of run time. That is more than one night: over 15 nights, about 6 h 49 min each. The Vespera Pro 2’s battery (rated about 11 h) should cover each night; 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 30WExternal bank extends the 11 h battery.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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How it frames
The Abell 39 is 2.9′ across. The Vespera Pro 2 frames 1.65° × 1.65° at 1.68″ per pixel, so it fills 3% 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; CovalENS mosaic gives 3.2° × 3.2° at 50 MP. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 30 h10,885 subs | 50 h17,858 subs | 130+ h48,336 subs |
| 20 s | 24 h4,387 subs | 44 h7,874 subs | 130+ h23,113 subs |
| 30 s | 22 h2,690 subs | 42 h5,015 subs | 130+ h15,174 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 30 h10,885 subs | 50 h17,858 subs | 130+ h48,336 subs |
| dual-band (Dual Band filter), clip-on | 38 h13,765 subs | 44 h15,900 subs | 70 h25,230 subs |
The Vespera Pro 2 has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. On an emission target like this it is the single biggest upgrade you can make.
About the Abell 39
A near-perfect faint sphere in Hercules. Very low surface brightness, an OIII target for dark skies and long dual-band stacks.
PN A66 39 · Planetary nebula in Hercules · magnitude 13.7 · 2.9′ · best in May, Jun, Jul. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
About the Vaonis Vespera Pro 2
The square-sensor 2026 Vespera with 2 µm pixels. Sharper than the Vespera 3 on small targets and correspondingly slower per pixel; the 12.5 MP square frame suits galaxies and planetaries.
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic gives 3.2° × 3.2° at 50 MP. 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 Abell 39 from a Vespera Pro 2? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Abell 39 with the ZWO Seestar S50: 22 h from Bortle 6
- Abell 39 with the ZWO Seestar S50 Pro: 24 h from Bortle 6
- Abell 39 with the ZWO Seestar S30: 26 h from Bortle 6
- Abell 39 with the ZWO Seestar S30 Pro: 26 h from Bortle 6
- Abell 39 with the DwarfLab DWARF 3: 26 h from Bortle 6
- Abell 39 with the DwarfLab DWARF mini: 21 h from Bortle 6
- Abell 39 with the DwarfLab Draco: 17 h from Bortle 6
- Abell 39 with the DwarfLab DWARF II: 130+ h from Bortle 6
- Abell 39 with the Vaonis Vespera II: 37 h from Bortle 6
- Abell 39 with the Vaonis Vespera Pro: 83 h from Bortle 6
- Abell 39 with the Vaonis Vespera 3: 35 h from Bortle 6
- Abell 39 with the Unistellar eQuinox 2: 34 h from Bortle 6
- Abell 39 with the Unistellar Odyssey: 160+ h from Bortle 6
- Abell 39 with the Celestron Origin: 9 h 41 min from Bortle 6
- Abell 39 with the Celestron Origin Mark II: 13 h from Bortle 6
All telescopes for the Abell 39 · All targets for the Vespera Pro 2