How long should I image the Omega Nebula with the Seestar S50 from a Bortle 6 sky?

About 23 min of total integration for a solid image, or 1 h 32 min for a showpiece. A quick look takes 6 min.

How many subs is that on the Seestar S50?

At the default 10 s sub length, 138 subs for a solid image from Bortle 6 and 105 from Bortle 3.

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

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 32 min to 23 min.

How long to image the Omega Nebula with the ZWO Seestar S50

From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 23 min (138 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Omega Nebula. A quick look takes 6 min; a showpiece 1 h 32 min. Under a Bortle 3 rural sky the solid figure drops to 17 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 26% of the frame’s short side.

Omega Nebula with the ZWO Seestar S50: 10 s subs with the built-in dual-band (LP filter) filter.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	4 min26 subs	17 min102 subs	1 h 07 min405 subs
Bortle 2Typical dark site	4 min26 subs	17 min103 subs	1 h 08 min409 subs
Bortle 3Rural	4 min27 subs	17 min105 subs	1 h 10 min418 subs
Bortle 4Rural / suburban transition	5 min28 subs	18 min110 subs	1 h 13 min439 subs
Bortle 5Suburban	5 min30 subs	20 min118 subs	1 h 18 min471 subs
Bortle 6Bright suburban	6 min35 subs	23 min138 subs	1 h 32 min552 subs
Bortle 7Suburban / urban transition	7 min45 subs	29 min177 subs	1 h 57 min705 subs
Bortle 8City	10 min59 subs	39 min236 subs	2 h 37 min944 subs
Bortle 9Inner city	15 min91 subs	1 h363 subs	4 h 02 min1,452 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 30 min of run time. The Seestar S50’s battery (rated about 6 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 power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
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Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks stray light.
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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 Omega Nebula is 11′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 26% of the frame’s short side.

Longer subs

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	17 min105 subs	20 min118 subs	29 min177 subs
20 s	14 min42 subs	16 min49 subs	26 min78 subs
30 s	15 min30 subs	15 min30 subs	25 min50 subs
60 s	30 min30 subs	30 min30 subs	30 min30 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
UV/IR-cut (no light-pollution filter)	14 min86 subs	21 min129 subs	53 min321 subs
dual-band (LP filter)	17 min105 subs	20 min118 subs	29 min177 subs

About the Omega Nebula

A bright, compact swan-shaped emission nebula, one of the brightest in the sky per unit area. Excellent from suburban skies.

M17, NGC 6618, Swan Nebula · Emission nebula in Sagittarius · magnitude 6.0 · 11′ · best in Jun, Jul, Aug. 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 ZWO Seestar S50

The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.

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 60 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 Seestar S50ZWO store Direct Amazon UK Amazon USThe ZWO 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 Omega Nebula with your Seestar S50? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Omega Nebula from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Omega Nebula · All targets for the Seestar S50