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

About 1 h 46 min of total integration for a solid image, or 7 h 02 min for a showpiece. A quick look takes 26 min.

How many subs is that on the Vespera Pro?

At the default 10 s sub length, 634 subs for a solid image from Bortle 6 and 281 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 1 h 46 min to 1 h 19 min.

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

From a Bortle 6 suburban sky, the Vaonis Vespera Pro needs about 1 h 46 min (634 subs of 10 s) for a solid image of the De Mairan's Nebula. A quick look takes 26 min; a showpiece 7 h 02 min. Under a Bortle 3 rural sky the solid figure drops to 47 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 21% of the frame’s short side.

De Mairan's Nebula with the Vaonis Vespera Pro: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	10 min62 subs	41 min247 subs	2 h 44 min985 subs
Bortle 2Typical dark site	11 min65 subs	43 min258 subs	2 h 52 min1,032 subs
Bortle 3Rural	12 min71 subs	47 min281 subs	3 h 07 min1,122 subs
Bortle 4Rural / suburban transition	14 min84 subs	56 min335 subs	3 h 43 min1,340 subs
Bortle 5Suburban	18 min106 subs	1 h 10 min422 subs	4 h 41 min1,686 subs
Bortle 6Bright suburban	26 min159 subs	1 h 46 min634 subs	7 h 02 min2,533 subs
Bortle 7Suburban / urban transition	43 min260 subs	2 h 53 min1,037 subs	12 h4,148 subs
Bortle 8City	1 h 09 min416 subs	4 h 37 min1,664 subs	18 h6,656 subs
Bortle 9Inner city	2 h 05 min751 subs	8 h 20 min3,001 subs	33 h12,004 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 17 min of run time. The Vespera Pro’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 30WExtends the 11 h battery; 30 W PD per Vaonis.
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How it frames

The De Mairan's Nebula is 20′ × 15′ across. The Vespera Pro frames 1.62° × 1.62° at 1.65″ per pixel, so it fills 21% 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	47 min281 subs	1 h 10 min422 subs	2 h 53 min1,037 subs
20 s	39 min118 subs	1 h 03 min189 subs	2 h 45 min497 subs
30 s	37 min74 subs	1 h121 subs	2 h 43 min326 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	47 min281 subs	1 h 10 min422 subs	2 h 53 min1,037 subs
dual-band (Dual Band filter), clip-on	1 h 01 min368 subs	1 h 08 min411 subs	1 h 40 min599 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 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 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.

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Imaged the De Mairan's Nebula with your Vespera Pro? 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 Pro? 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 Pro