How long to image the NGC 6781 with the Vaonis Vespera II
From a Bortle 6 suburban sky, the Vaonis Vespera II needs about 4 h 15 min (1,532 subs of 10 s) for a solid image of the NGC 6781. A quick look takes 1 h 04 min; a showpiece 17 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 37 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 is small in the frame, about 45 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 20 min123 subs | 1 h 22 min491 subs | 5 h 27 min1,964 subs |
| Bortle 2Typical dark site | 22 min131 subs | 1 h 27 min523 subs | 5 h 48 min2,091 subs |
| Bortle 3Rural | 24 min146 subs | 1 h 37 min584 subs | 6 h 29 min2,333 subs |
| Bortle 4Rural / suburban transition | 30 min183 subs | 2 h 02 min730 subs | 8 h 06 min2,919 subs |
| Bortle 5Suburban | 40 min241 subs | 2 h 40 min962 subs | 11 h3,848 subs |
| Bortle 6Bright suburban | 1 h 04 min383 subs | 4 h 15 min1,532 subs | 17 h6,126 subs |
| Bortle 7Suburban / urban transition | 1 h 49 min655 subs | 7 h 16 min2,617 subs | 29 h10,468 subs |
| Bortle 8City | 2 h 59 min1,076 subs | 12 h4,303 subs | 48 h17,209 subs |
| Bortle 9Inner city | 5 h 29 min1,975 subs | 22 h7,897 subs | 88 h31,585 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 5 h 32 min of run time. The Vespera II’s battery is rated at about 4 h, so the session 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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Everything that fits the Vespera II →
How it frames
The NGC 6781 is 1.8′ across. The Vespera II frames 2.55° × 1.44° at 2.39″ per pixel, so it is small in the frame, about 45 pixels across. It is worth doing, but the result is a crop rather than a full frame; a longer focal length would resolve more of it.
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 | 1 h 37 min584 subs | 2 h 40 min962 subs | 7 h 16 min2,617 subs |
| 20 s | 1 h 22 min248 subs | 2 h 26 min437 subs | 7 h 01 min1,265 subs |
| 30 s | 1 h 17 min155 subs | 2 h 21 min282 subs | 6 h 56 min833 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| No filter | 1 h 37 min584 subs | 2 h 40 min962 subs | 7 h 16 min2,617 subs |
| dual-band (Dual Band filter), clip-on | 1 h 54 min683 subs | 2 h 13 min799 subs | 3 h 37 min1,305 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 NGC 6781
A ghostly ring planetary in Aquila, larger and fainter than the Ring Nebula. Dual-band recommended.
Aquila planetary · Planetary nebula in Aquila · magnitude 11.4 · 1.8′ · best in Jun, Jul, Aug. 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 NGC 6781 from a Vespera II? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 6781 with the ZWO Seestar S50: 2 h 42 min from Bortle 6
- NGC 6781 with the ZWO Seestar S50 Pro: 3 h 02 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30: 3 h 09 min from Bortle 6
- NGC 6781 with the ZWO Seestar S30 Pro: 3 h 16 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF 3: 3 h 22 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF mini: 2 h 40 min from Bortle 6
- NGC 6781 with the DwarfLab Draco: 2 h 08 min from Bortle 6
- NGC 6781 with the DwarfLab DWARF II: 15 h from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro: 9 h 32 min from Bortle 6
- NGC 6781 with the Vaonis Vespera 3: 4 h 04 min from Bortle 6
- NGC 6781 with the Vaonis Vespera Pro 2: 9 h 05 min from Bortle 6
- NGC 6781 with the Unistellar eQuinox 2: 3 h 52 min from Bortle 6
- NGC 6781 with the Unistellar Odyssey: 18 h from Bortle 6
- NGC 6781 with the Celestron Origin: 1 h 07 min from Bortle 6
- NGC 6781 with the Celestron Origin Mark II: 1 h 33 min from Bortle 6
All telescopes for the NGC 6781 · All targets for the Vespera II