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

About 5 h 21 min of total integration for a solid image, or 21 h for a showpiece. A quick look takes 1 h 20 min.

How many subs is that on the Seestar S30 Pro?

At the default 10 s sub length, 1,927 subs for a solid image from Bortle 6 and 722 from Bortle 3.

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

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

How long to image the Pinwheel Galaxy with the ZWO Seestar S30 Pro

From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 5 h 21 min (1,927 subs of 10 s) for a solid image of the Pinwheel Galaxy. A quick look takes 1 h 20 min; a showpiece 21 h. Under a Bortle 3 rural sky the solid figure drops to 2 h. 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 22% of the frame’s short side.

Pinwheel Galaxy with the ZWO Seestar S30 Pro: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	25 min152 subs	1 h 41 min605 subs	6 h 43 min2,418 subs
Bortle 2Typical dark site	27 min162 subs	1 h 48 min646 subs	7 h 10 min2,581 subs
Bortle 3Rural	30 min181 subs	2 h722 subs	8 h 01 min2,888 subs
Bortle 4Rural / suburban transition	38 min227 subs	2 h 31 min908 subs	10 h3,632 subs
Bortle 5Suburban	50 min301 subs	3 h 20 min1,203 subs	13 h4,812 subs
Bortle 6Bright suburban	1 h 20 min482 subs	5 h 21 min1,927 subs	21 h7,706 subs
Bortle 7Suburban / urban transition	2 h 18 min827 subs	9 h 11 min3,306 subs	37 h13,221 subs
Bortle 8City	3 h 47 min1,362 subs	15 h5,446 subs	61 h21,783 subs
Bortle 9Inner city	6 h 57 min2,503 subs	28 h10,011 subs	110+ h40,044 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 6 h 57 min of run time. The Seestar S30 Pro’s battery is rated at about 5 h, so the session needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)

USB-C power bank 10000mAh 5V 3A5 V 3 A input and it runs while charging.
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Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
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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 Pinwheel Galaxy is 29′ × 27′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 22% 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 length	Bortle 3	Bortle 5	Bortle 7
10 s	2 h722 subs	3 h 20 min1,203 subs	9 h 11 min3,306 subs
20 s	1 h 39 min297 subs	2 h 59 min538 subs	8 h 49 min1,589 subs
30 s	1 h 32 min184 subs	2 h 52 min344 subs	8 h 42 min1,045 subs
60 s	1 h 25 min85 subs	2 h 45 min165 subs	8 h 35 min516 subs

Leave the dual-band filter out for the Pinwheel 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 Pinwheel Galaxy

Big, face-on and faint. Its total magnitude is flattering; spread over half a degree the arms are dim and demand hours, especially from suburban skies.

M101, NGC 5457 · Galaxy in Ursa Major · magnitude 7.9 · 29′ × 27′ · best in Apr, May, Jun. 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.

Where to buy the Seestar S30 ProZWO 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 Pinwheel 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 Pinwheel 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 Pinwheel Galaxy · All targets for the Seestar S30 Pro