How long should I image the NGC 6781 with the Vespera 3 from a Bortle 6 sky?

About 4 h 04 min of total integration for a solid image, or 16 h for a showpiece. A quick look takes 1 h 01 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 1,463 subs for a solid image from Bortle 6 and 553 from Bortle 3.

Does a dual-band filter help on the NGC 6781?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 4 h 04 min to 2 h 33 min.

How long to image the NGC 6781 with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 4 h 04 min (1,463 subs of 10 s) for a solid image of the NGC 6781. A quick look takes 1 h 01 min; a showpiece 16 h. Under a Bortle 3 rural sky the solid figure drops to 1 h 32 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 44 pixels across.

NGC 6781 with the Vaonis Vespera 3: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	19 min116 subs	1 h 17 min464 subs	5 h 09 min1,853 subs
Bortle 2Typical dark site	21 min124 subs	1 h 22 min494 subs	5 h 29 min1,976 subs
Bortle 3Rural	23 min139 subs	1 h 32 min553 subs	6 h 08 min2,209 subs
Bortle 4Rural / suburban transition	29 min174 subs	1 h 55 min693 subs	7 h 42 min2,771 subs
Bortle 5Suburban	38 min229 subs	2 h 33 min916 subs	10 h3,663 subs
Bortle 6Bright suburban	1 h 01 min366 subs	4 h 04 min1,463 subs	16 h5,851 subs
Bortle 7Suburban / urban transition	1 h 44 min627 subs	6 h 58 min2,506 subs	28 h10,021 subs
Bortle 8City	2 h 52 min1,031 subs	11 h4,124 subs	46 h16,495 subs
Bortle 9Inner city	5 h 16 min1,894 subs	21 h7,576 subs	84 h30,302 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 5 h 17 min of run time. The Vespera 3’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 30WVaonis says an external bank extends sessions; 30 W PD as for the II and Pro.
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Everything that fits the Vespera 3 →

How it frames

The NGC 6781 is 1.8′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it is small in the frame, about 44 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; CovalENS mosaic widens the field to 4.3° × 2.4°. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	1 h 32 min553 subs	2 h 33 min916 subs	6 h 58 min2,506 subs
20 s	1 h 18 min236 subs	2 h 19 min417 subs	6 h 44 min1,212 subs
30 s	1 h 14 min148 subs	2 h 14 min269 subs	6 h 39 min799 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	1 h 32 min553 subs	2 h 33 min916 subs	6 h 58 min2,506 subs
dual-band (Dual Band filter), clip-on	1 h 46 min639 subs	2 h 05 min751 subs	3 h 26 min1,237 subs

The Vespera 3 has no built-in dual-band filter. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. The new optical baffle is not a substitute for a CLS filter. 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 3

The 2026 Vespera: same 50 mm quadruplet class as the II on an 8 MP IMX585, with a 24 MP mosaic mode and 11 hours of battery. Per pixel it behaves like a Seestar S50 Pro without the built-in dual-band filter.

10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic widens the field to 4.3° × 2.4°. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. The new optical baffle is not a substitute for a CLS filter.

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.

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Imaged the NGC 6781 with your Vespera 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the NGC 6781 from a Vespera 3? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the NGC 6781 · All targets for the Vespera 3