How long should I image the Andromeda Galaxy with the Seestar S30 from a Bortle 6 sky?

About 1 h 32 min of total integration for a solid image, or 6 h 08 min for a showpiece. A quick look takes 23 min.

How many subs is that on the Seestar S30?

At the default 10 s sub length, 552 subs for a solid image from Bortle 6 and 231 from Bortle 3.

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

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

How long to image the Andromeda Galaxy with the ZWO Seestar S30

From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 1 h 32 min (552 subs of 10 s) for a solid image of the Andromeda Galaxy. A quick look takes 23 min; a showpiece 6 h 08 min. Under a Bortle 3 rural sky the solid figure drops to 38 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 is 2.5× wider than the frame.

Andromeda Galaxy with the ZWO Seestar S30: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	8 min50 subs	33 min199 subs	2 h 12 min795 subs
Bortle 2Typical dark site	9 min53 subs	35 min210 subs	2 h 20 min839 subs
Bortle 3Rural	10 min58 subs	38 min231 subs	2 h 33 min921 subs
Bortle 4Rural / suburban transition	12 min70 subs	47 min280 subs	3 h 06 min1,119 subs
Bortle 5Suburban	15 min90 subs	1 h359 subs	3 h 59 min1,434 subs
Bortle 6Bright suburban	23 min138 subs	1 h 32 min552 subs	6 h 08 min2,206 subs
Bortle 7Suburban / urban transition	38 min230 subs	2 h 33 min920 subs	10 h3,678 subs
Bortle 8City	1 h 02 min373 subs	4 h 08 min1,491 subs	17 h5,963 subs
Bortle 9Inner city	1 h 53 min678 subs	7 h 31 min2,709 subs	30 h10,835 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 59 min of run time. The Seestar S30’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 10000mAh 5V 3A6,000 mAh inside; a 10,000 mAh 5 V 3 A bank roughly doubles a session.
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Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and 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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Everything that fits the Seestar S30 →

How it frames

The Andromeda Galaxy is 178′ × 63′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it is 2.5× wider than the frame. A mosaic, or choosing the part you want and letting the rest go, is how it gets shot on this scope.

Longer subs

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	38 min231 subs	1 h359 subs	2 h 33 min920 subs
20 s	31 min94 subs	53 min158 subs	2 h 26 min439 subs
30 s	29 min58 subs	50 min101 subs	2 h 24 min288 subs
60 s	30 min30 subs	48 min48 subs	2 h 21 min142 subs

Leave the dual-band filter out for the Andromeda 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 13 times slower.

About the Andromeda Galaxy

The nearest big spiral and the most imaged galaxy in the sky. The core arrives in minutes, the dust lanes in an hour, the faint outer disc needs a whole night. Too big for most smart-scope fields without mosaic.

M31, NGC 224 · Galaxy in Andromeda · magnitude 3.4 · 178′ × 63′ · 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 S30

Wider and lighter than the S50 with the same 2.9 µm pixels, so its per-pixel speed on extended targets is close despite the smaller aperture. Ideal for big nebulae.

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters.

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 S30ZWO 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 Andromeda Galaxy with your Seestar S30? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Andromeda Galaxy from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Andromeda Galaxy · All targets for the Seestar S30