How long should I image the Sculptor Galaxy with the Seestar S50 from a Bortle 6 sky?

About 29 min of total integration for a solid image, or 1 h 57 min for a showpiece. A quick look takes 7 min.

How many subs is that on the Seestar S50?

At the default 10 s sub length, 175 subs for a solid image from Bortle 6 and 75 from Bortle 3.

Does a dual-band filter help on the Sculptor Galaxy?

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

How long to image the Sculptor Galaxy with the ZWO Seestar S50

From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 29 min (175 subs of 10 s) for a solid image of the Sculptor Galaxy. A quick look takes 7 min; a showpiece 1 h 57 min. Under a Bortle 3 rural sky the solid figure drops to 12 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 63% of the frame’s short side.

Sculptor Galaxy 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	3 min17 subs	11 min66 subs	43 min261 subs
Bortle 2Typical dark site	3 min18 subs	11 min69 subs	46 min274 subs
Bortle 3Rural	3 min19 subs	12 min75 subs	50 min300 subs
Bortle 4Rural / suburban transition	4 min23 subs	15 min91 subs	1 h362 subs
Bortle 5Suburban	5 min29 subs	19 min115 subs	1 h 17 min460 subs
Bortle 6Bright suburban	7 min44 subs	29 min175 subs	1 h 57 min700 subs
Bortle 7Suburban / urban transition	12 min73 subs	48 min290 subs	3 h 13 min1,159 subs
Bortle 8City	19 min117 subs	1 h 18 min468 subs	5 h 12 min1,870 subs
Bortle 9Inner city	35 min212 subs	2 h 21 min847 subs	9 h 25 min3,388 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 38 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 Sculptor Galaxy is 27′ × 7′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it fills 63% 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	12 min75 subs	19 min115 subs	48 min290 subs
20 s	11 min33 subs	18 min53 subs	47 min141 subs
30 s	15 min30 subs	17 min35 subs	46 min93 subs
60 s	30 min30 subs	30 min30 subs	46 min46 subs

Leave the dual-band filter out for the Sculptor Galaxy. 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 Sculptor Galaxy

A big, dusty, nearly edge-on starburst galaxy, superb from the south and low but possible from mid-northern latitudes.

NGC 253, Caldwell 65, Silver Coin · Galaxy in Sculptor · magnitude 7.2 · 27′ × 7′ · best in Sep, Oct, Nov. 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 Sculptor Galaxy with your Seestar S50? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Sculptor Galaxy 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 Sculptor Galaxy · All targets for the Seestar S50