How long should I image the Antennae Galaxies with the Seestar S50 from a Bortle 6 sky?

About 2 h of total integration for a solid image, or 7 h 59 min for a showpiece. A quick look takes 30 min.

How many subs is that on the Seestar S50?

At the default 10 s sub length, 719 subs for a solid image from Bortle 6 and 290 from Bortle 3.

Does a dual-band filter help on the Antennae Galaxies?

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

How long to image the Antennae Galaxies with the ZWO Seestar S50

From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 2 h (719 subs of 10 s) for a solid image of the Antennae Galaxies. A quick look takes 30 min; a showpiece 7 h 59 min. Under a Bortle 3 rural sky the solid figure drops to 48 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 12% of the frame’s short side.

Antennae Galaxies with the ZWO Seestar S50: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	10 min63 subs	41 min249 subs	2 h 45 min993 subs
Bortle 2Typical dark site	11 min66 subs	44 min263 subs	2 h 55 min1,051 subs
Bortle 3Rural	12 min73 subs	48 min290 subs	3 h 13 min1,160 subs
Bortle 4Rural / suburban transition	15 min90 subs	59 min357 subs	3 h 57 min1,425 subs
Bortle 5Suburban	19 min116 subs	1 h 17 min461 subs	5 h 07 min1,844 subs
Bortle 6Bright suburban	30 min180 subs	2 h719 subs	7 h 59 min2,874 subs
Bortle 7Suburban / urban transition	50 min303 subs	3 h 21 min1,209 subs	13 h4,836 subs
Bortle 8City	1 h 22 min493 subs	5 h 28 min1,971 subs	22 h7,881 subs
Bortle 9Inner city	2 h 30 min899 subs	9 h 59 min3,595 subs	40 h14,377 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 36 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 Antennae Galaxies is 5′ × 3′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 12% 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	48 min290 subs	1 h 17 min461 subs	3 h 21 min1,209 subs
20 s	42 min125 subs	1 h 10 min211 subs	3 h 15 min585 subs
30 s	39 min79 subs	1 h 08 min136 subs	3 h 13 min386 subs
60 s	37 min38 subs	1 h 06 min66 subs	3 h 10 min191 subs

Leave the dual-band filter out for the Antennae Galaxies. It is a galaxy, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 12 times slower.

About the Antennae Galaxies

Two colliding galaxies with long tidal tails. The cores are reachable; the antennae themselves are a dark-sky, long-integration task.

NGC 4038 and NGC 4039, Caldwell 60/61 · Galaxy in Corvus · magnitude 10.3 · 5′ × 3′ · best in Mar, Apr, May. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.

Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.

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 Antennae Galaxies with your Seestar S50? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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

Same target, other telescopes

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