How long to image the Abell 39 with the Vaonis Vespera Pro
From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 83 h (29,755 subs of 10 s) for a solid image of the Abell 39. A quick look takes 21 h; a showpiece 330+ h. Under a Bortle 3 rural sky the solid figure drops to 32 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 48 min2,450 subs | 27 h9,799 subs | 110+ h39,196 subs |
| Bortle 2Typical dark site | 7 h 14 min2,603 subs | 29 h10,412 subs | 120+ h41,647 subs |
| Bortle 3Rural | 8 h 02 min2,893 subs | 32 h11,572 subs | 130+ h46,285 subs |
| Bortle 4Rural / suburban transition | 9 h 59 min3,595 subs | 40 h14,380 subs | 160+ h57,520 subs |
| Bortle 5Suburban | 13 h4,708 subs | 52 h18,832 subs | 210+ h75,327 subs |
| Bortle 6Bright suburban | 21 h7,439 subs | 83 h29,755 subs | 330+ h119,017 subs |
| Bortle 7Suburban / urban transition | 35 h12,642 subs | 140+ h50,567 subs | 560+ h202,267 subs |
| Bortle 8City | 58 h20,721 subs | 230+ h82,881 subs | 920+ h331,524 subs |
| Bortle 9Inner city | 110+ h37,950 subs | 420+ h151,798 subs | 1690+ h607,190 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 110+ h of run time. That is more than one night: over 16 nights, about 6 h 43 min each. The Vespera Pro’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 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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How it frames
The Abell 39 is 2.9′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ 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, no EQ mode. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 32 h11,572 subs | 52 h18,832 subs | 140+ h50,567 subs |
| 20 s | 26 h4,642 subs | 46 h8,272 subs | 130+ h24,140 subs |
| 30 s | 24 h2,840 subs | 44 h5,261 subs | 130+ h15,839 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 32 h11,572 subs | 52 h18,832 subs | 140+ h50,567 subs |
| dual-band (Dual Band filter), clip-on | 41 h14,818 subs | 47 h17,041 subs | 74 h26,756 subs |
The Vespera Pro 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
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 Abell 39 from a Vespera Pro? 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 3: 35 h from Bortle 6
- Abell 39 with the Vaonis Vespera Pro 2: 79 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