How long should I image the De Mairan's Nebula with the Vespera 3 from a Bortle 6 sky?

About 45 min of total integration for a solid image, or 3 h for a showpiece. A quick look takes 11 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 271 subs for a solid image from Bortle 6 and 110 from Bortle 3.

Does a dual-band filter help on the De Mairan's Nebula?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 45 min to 30 min.

How long to image the De Mairan's Nebula with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 45 min (271 subs of 10 s) for a solid image of the De Mairan's Nebula. A quick look takes 11 min; a showpiece 3 h. Under a Bortle 3 rural sky the solid figure drops to 18 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 fills 23% of the frame’s short side.

De Mairan's Nebula 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	4 min24 subs	16 min94 subs	1 h 03 min376 subs
Bortle 2Typical dark site	4 min25 subs	17 min100 subs	1 h 06 min398 subs
Bortle 3Rural	5 min28 subs	18 min110 subs	1 h 13 min439 subs
Bortle 4Rural / suburban transition	6 min34 subs	22 min135 subs	1 h 30 min538 subs
Bortle 5Suburban	7 min44 subs	29 min174 subs	1 h 56 min696 subs
Bortle 6Bright suburban	11 min68 subs	45 min271 subs	3 h1,083 subs
Bortle 7Suburban / urban transition	19 min114 subs	1 h 16 min456 subs	5 h 03 min1,821 subs
Bortle 8City	31 min186 subs	2 h 04 min742 subs	8 h 14 min2,967 subs
Bortle 9Inner city	56 min339 subs	3 h 45 min1,353 subs	15 h5,410 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 59 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, and 30% off the battery for a December night.)

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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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 De Mairan's Nebula is 20′ × 15′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 23% 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 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	18 min110 subs	29 min174 subs	1 h 16 min456 subs
20 s	16 min48 subs	27 min80 subs	1 h 13 min221 subs
30 s	15 min31 subs	26 min52 subs	1 h 13 min146 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	18 min110 subs	29 min174 subs	1 h 16 min456 subs
dual-band (Dual Band filter), clip-on	22 min131 subs	25 min150 subs	39 min236 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 De Mairan's Nebula

The comma-shaped nebula north of the Orion Nebula's core, split from it by a dark lane. Always in the same frame as M42.

M43, NGC 1982 · Emission nebula in Orion · magnitude 9.0 · 20′ × 15′ · best in Nov, Dec, Jan. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.

Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.

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 De Mairan's Nebula with your Vespera 3? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the De Mairan's Nebula 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 De Mairan's Nebula · All targets for the Vespera 3