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

About 25 min of total integration for a solid image, or 1 h 38 min for a showpiece. A quick look takes 6 min.

How many subs is that on the Seestar S30?

At the default 10 s sub length, 148 subs for a solid image from Bortle 6 and 75 from Bortle 3.

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

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

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

From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 25 min (148 subs of 10 s) for a solid image of the Spindle Galaxy. A quick look takes 6 min; a showpiece 1 h 38 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 7% of the frame’s short side.

Spindle 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	3 min17 subs	11 min68 subs	45 min271 subs
Bortle 2Typical dark site	3 min18 subs	12 min71 subs	47 min281 subs
Bortle 3Rural	3 min19 subs	12 min75 subs	50 min299 subs
Bortle 4Rural / suburban transition	4 min22 subs	14 min86 subs	57 min344 subs
Bortle 5Suburban	4 min26 subs	17 min104 subs	1 h 09 min415 subs
Bortle 6Bright suburban	6 min37 subs	25 min148 subs	1 h 38 min590 subs
Bortle 7Suburban / urban transition	10 min58 subs	38 min231 subs	2 h 34 min923 subs
Bortle 8City	15 min90 subs	1 h360 subs	4 h1,439 subs
Bortle 9Inner city	26 min159 subs	1 h 46 min636 subs	7 h 03 min2,541 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 32 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.
Amazon UK Amazon US
Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and stray light.
Amazon UK Amazon US
red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
Amazon UK Amazon US

Affiliate links: the retailer pays us a small commission and you pay the same price. These are search links to the named product, not endorsements of a particular listing; check the listing matches your model.

Everything that fits the Seestar S30 →

How it frames

The Spindle Galaxy is 4.7′ × 1.9′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 7% 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	12 min75 subs	17 min104 subs	38 min231 subs
20 s	11 min33 subs	16 min47 subs	37 min111 subs
30 s	15 min30 subs	15 min31 subs	36 min73 subs
60 s	30 min30 subs	30 min30 subs	36 min36 subs

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

An edge-on lenticular with a thin dust lane. Small, but its surface brightness is decent.

M102, NGC 5866 · Galaxy in Draco · magnitude 9.9 · 4.7′ × 1.9′ · 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

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 Spindle 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 Spindle 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 Spindle Galaxy · All targets for the Seestar S30