How long to image the Bode's Galaxy with the ZWO Seestar S30 Pro

From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 1 h 14 min (444 subs of 10 s) for a solid image of the Bode's Galaxy. A quick look takes 18 min; a showpiece 4 h 55 min. Under a Bortle 3 rural sky the solid figure drops to 30 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.

Bode's Galaxy with the ZWO Seestar S30 Pro: 10 s subs.
SkyQuick lookTarget obvious, still noisySolidClean enough to shareShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site6 min39 subs26 min156 subs1 h 44 min622 subs
Bortle 2Typical dark site7 min42 subs27 min165 subs1 h 50 min658 subs
Bortle 3Rural8 min46 subs30 min182 subs2 h 01 min725 subs
Bortle 4Rural / suburban transition9 min56 subs37 min222 subs2 h 28 min887 subs
Bortle 5Suburban12 min72 subs48 min286 subs3 h 10 min1,143 subs
Bortle 6Bright suburban18 min111 subs1 h 14 min444 subs4 h 55 min1,773 subs
Bortle 7Suburban / urban transition31 min186 subs2 h 04 min744 subs8 h 16 min2,974 subs
Bortle 8City50 min303 subs3 h 22 min1,210 subs13 h4,837 subs
Bortle 9Inner city1 h 32 min551 subs6 h 07 min2,203 subs24 h8,812 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 36 min of run time. The Seestar S30 Pro’s battery (rated about 5 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, and 30% off the battery for a February night.)

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How it frames

The Bode's Galaxy is 27′ × 14′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 20% of the frame’s short side.

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 lengthBortle 3Bortle 5Bortle 7
10 s30 min182 subs48 min286 subs2 h 04 min744 subs
20 s26 min77 subs43 min129 subs1 h 59 min358 subs
30 s24 min48 subs41 min83 subs1 h 58 min236 subs
60 s30 min30 subs40 min40 subs1 h 56 min117 subs

Leave the dual-band filter out for the Bode's 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 Bode's Galaxy

A big, bright grand-design spiral that circles the pole for northern imagers, so it is available all year. Shares a frame with M82.

M81, NGC 3031 · Galaxy in Ursa Major · magnitude 6.9 · 27′ × 14′ · best in Jan, Feb, Mar. 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 Pro

The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.

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 on the telephoto camera.

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.

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Imaged the Bode's Galaxy with your Seestar S30 Pro? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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

Same target, other telescopes

All telescopes for the Bode's Galaxy · All targets for the Seestar S30 Pro