How long to image the Bode's Galaxy with the ZWO Seestar S50 Pro

From a Bortle 6 suburban sky, the ZWO Seestar S50 Pro needs about 1 h 10 min (419 subs of 10 s) for a solid image of the Bode's Galaxy. A quick look takes 17 min; a showpiece 4 h 39 min. Under a Bortle 3 rural sky the solid figure drops to 28 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 33% of the frame’s short side.

Bode's Galaxy with the ZWO Seestar S50 Pro: 10 s subs.
SkyQuick lookTarget obvious, still noisySolidClean enough to shareShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site6 min37 subs24 min145 subs1 h 36 min579 subs
Bortle 2Typical dark site6 min39 subs26 min154 subs1 h 42 min613 subs
Bortle 3Rural7 min43 subs28 min169 subs1 h 53 min676 subs
Bortle 4Rural / suburban transition9 min52 subs35 min208 subs2 h 18 min830 subs
Bortle 5Suburban11 min68 subs45 min269 subs2 h 59 min1,074 subs
Bortle 6Bright suburban17 min105 subs1 h 10 min419 subs4 h 39 min1,673 subs
Bortle 7Suburban / urban transition29 min176 subs1 h 57 min704 subs7 h 49 min2,814 subs
Bortle 8City48 min287 subs3 h 11 min1,147 subs13 h4,586 subs
Bortle 9Inner city1 h 27 min523 subs5 h 48 min2,091 subs23 h8,364 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 31 min of run time. The Seestar S50 Pro’s battery (rated about 9 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 S50 Pro frames 2.45° × 1.38° at 2.30″ per pixel, so it fills 33% of the frame’s short side.

Longer subs

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

Sub lengthBortle 3Bortle 5Bortle 7
10 s28 min169 subs45 min269 subs1 h 57 min704 subs
20 s24 min72 subs41 min122 subs1 h 53 min340 subs
30 s23 min46 subs39 min79 subs1 h 52 min224 subs
60 s30 min30 subs38 min38 subs1 h 50 min111 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 S50 Pro

The S50 optics at 260 mm on an 8 MP 1/1.2-inch sensor: a wider, taller field, four times the pixels, and 60 s subs in EQ mode. Per pixel it is a whisker slower than the S50 because of the longer focal length; the long subs make it the better dark-site scope.

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, and 60 s is the ceiling. 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 S50 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 S50 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 S50 Pro