How long should I image the Iris Nebula with the Vespera 3 from a Bortle 6 sky?

About 1 h 48 min of total integration for a solid image, or 7 h 13 min for a showpiece. A quick look takes 27 min.

How many subs is that on the Vespera 3?

At the default 10 s sub length, 651 subs for a solid image from Bortle 6 and 246 from Bortle 3.

Does a dual-band filter help on the Iris Nebula?

No. The Iris Nebula is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the Iris Nebula with the Vaonis Vespera 3

From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 1 h 48 min (651 subs of 10 s) for a solid image of the Iris Nebula. A quick look takes 27 min; a showpiece 7 h 13 min. Under a Bortle 3 rural sky the solid figure drops to 41 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 20% of the frame’s short side.

Iris 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	9 min52 subs	34 min206 subs	2 h 17 min824 subs
Bortle 2Typical dark site	9 min55 subs	37 min220 subs	2 h 26 min879 subs
Bortle 3Rural	10 min62 subs	41 min246 subs	2 h 44 min982 subs
Bortle 4Rural / suburban transition	13 min77 subs	51 min308 subs	3 h 25 min1,232 subs
Bortle 5Suburban	17 min102 subs	1 h 08 min407 subs	4 h 31 min1,628 subs
Bortle 6Bright suburban	27 min163 subs	1 h 48 min651 subs	7 h 13 min2,601 subs
Bortle 7Suburban / urban transition	46 min279 subs	3 h 06 min1,114 subs	12 h4,454 subs
Bortle 8City	1 h 16 min459 subs	5 h 05 min1,833 subs	20 h7,331 subs
Bortle 9Inner city	2 h 20 min842 subs	9 h 21 min3,367 subs	37 h13,468 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 21 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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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 Iris Nebula is 18′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 20% 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	41 min246 subs	1 h 08 min407 subs	3 h 06 min1,114 subs
20 s	35 min105 subs	1 h 02 min186 subs	3 h539 subs
30 s	33 min66 subs	1 h120 subs	2 h 57 min355 subs

About the Iris Nebula

A blue reflection nebula wrapped in dark dust. No filter helps, and the surrounding dust needs a dark sky and hours.

NGC 7023, Caldwell 4 · Reflection nebula in Cepheus · magnitude 6.8 · 18′ · best in Jul, Aug, Sep. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.

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.

Where to buy the Vespera 3Vaonis store Direct Amazon UK Amazon USThe Vaonis store link is a plain link; the others are affiliate links. As an Amazon Associate I earn from qualifying purchases, at no cost to you.

Imaged the Iris 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 Iris 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 Iris Nebula · All targets for the Vespera 3