How long to image the Abell 39 with the Vaonis Vespera II
From a Bortle 6 suburban sky, the Vaonis Vespera II needs about 37 h (13,236 subs of 10 s) for a solid image of the Abell 39. A quick look takes 9 h 11 min; a showpiece 150+ h. Under a Bortle 3 rural sky the solid figure drops to 13 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 | 2 h 36 min937 subs | 10 h3,745 subs | 42 h14,979 subs |
| Bortle 2Typical dark site | 2 h 48 min1,010 subs | 11 h4,037 subs | 45 h16,145 subs |
| Bortle 3Rural | 3 h 11 min1,147 subs | 13 h4,588 subs | 51 h18,351 subs |
| Bortle 4Rural / suburban transition | 4 h 07 min1,481 subs | 16 h5,924 subs | 66 h23,695 subs |
| Bortle 5Suburban | 5 h 35 min2,011 subs | 22 h8,041 subs | 89 h32,164 subs |
| Bortle 6Bright suburban | 9 h 11 min3,309 subs | 37 h13,236 subs | 150+ h52,944 subs |
| Bortle 7Suburban / urban transition | 16 h5,784 subs | 64 h23,135 subs | 260+ h92,540 subs |
| Bortle 8City | 27 h9,627 subs | 110+ h38,505 subs | 430+ h154,018 subs |
| Bortle 9Inner city | 50 h17,821 subs | 200+ h71,283 subs | 790+ h285,131 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 48 h of run time. That is more than one night: over 7 nights, about 6 h 50 min each. The Vespera II’s battery is rated at about 4 h, so each night needs an external power bank. (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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How it frames
The Abell 39 is 2.9′ across. The Vespera II frames 2.55° × 1.44° at 2.39″ 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 | 13 h4,588 subs | 22 h8,041 subs | 64 h23,135 subs |
| 20 s | 10 h1,890 subs | 20 h3,616 subs | 62 h11,163 subs |
| 30 s | 9 h 45 min1,170 subs | 19 h2,321 subs | 61 h7,353 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 13 h4,588 subs | 22 h8,041 subs | 64 h23,135 subs |
| dual-band (Dual Band filter), clip-on | 14 h5,179 subs | 17 h6,236 subs | 30 h10,857 subs |
The Vespera II has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar; the app detects which is fitted. 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 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 Abell 39 from a Vespera II? 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 Pro: 83 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 II