How long should I image the Witch Head Nebula with the Seestar S50 from a Bortle 6 sky?

About 41 h of total integration for a solid image, or 160+ h for a showpiece. A quick look takes 10 h.

How many subs is that on the Seestar S50?

At the default 10 s sub length, 14,628 subs for a solid image from Bortle 6 and 4,973 from Bortle 3.

Does a dual-band filter help on the Witch Head Nebula?

No. The Witch Head Nebula is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the Witch Head Nebula with the ZWO Seestar S50

From a Bortle 6 suburban sky, the ZWO Seestar S50 needs about 41 h (14,628 subs of 10 s) for a solid image of the Witch Head Nebula. A quick look takes 10 h; a showpiece 160+ h. Under a Bortle 3 rural sky the solid figure drops to 14 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 is 4.2× wider than the frame.

Witch Head Nebula with the ZWO Seestar S50: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	2 h 48 min1,008 subs	11 h4,032 subs	45 h16,126 subs
Bortle 2Typical dark site	3 h 02 min1,090 subs	12 h4,357 subs	48 h17,428 subs
Bortle 3Rural	3 h 27 min1,244 subs	14 h4,973 subs	55 h19,890 subs
Bortle 4Rural / suburban transition	4 h 29 min1,616 subs	18 h6,464 subs	72 h25,856 subs
Bortle 5Suburban	6 h 08 min2,207 subs	25 h8,828 subs	98 h35,311 subs
Bortle 6Bright suburban	10 h3,657 subs	41 h14,628 subs	160+ h58,510 subs
Bortle 7Suburban / urban transition	18 h6,420 subs	71 h25,679 subs	290+ h102,714 subs
Bortle 8City	30 h10,710 subs	120+ h42,837 subs	480+ h171,348 subs
Bortle 9Inner city	55 h19,858 subs	220+ h79,431 subs	880+ h317,722 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 53 h of run time. That is more than one night: over 8 nights, about 6 h 36 min each. The Seestar S50’s battery is rated at about 6 h, less near freezing, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a December night.)

USB-C power bank 20000mAh 5V 3AThe S50 draws 5 V 3 A over USB-C and runs while charging; no PD needed.
Amazon UK Amazon US
Seestar S50 dew shieldThe built-in heater copes with most nights; a shield helps in heavy dew and blocks 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
hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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 S50 →

How it frames

The Witch Head Nebula is 180′ × 60′ across. The Seestar S50 frames 1.28° × 0.72° at 2.39″ per pixel, so it is 4.2× 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 (app 2.5 and later). Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	14 h4,973 subs	25 h8,828 subs	71 h25,679 subs
20 s	11 h2,035 subs	22 h3,963 subs	69 h12,388 subs
30 s	10 h1,257 subs	21 h2,542 subs	68 h8,159 subs
60 s	9 h 38 min578 subs	20 h1,221 subs	67 h4,029 subs

Leave the dual-band filter out for the Witch Head Nebula. It is a reflection nebula, 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 Witch Head Nebula

A very faint blue reflection nebula lit by Rigel. A dark-sky, all-night, broadband project; it is one of the hardest objects on this list.

IC 2118 · Reflection nebula in Eridanus · magnitude 13.0 · 180′ × 60′ · best in Nov, Dec, Jan. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Reflection nebulae are starlight scattered by dust, so they are broadband and blue. A dual-band filter removes almost all of it; do not use one. These are among the faintest structures a smart scope can attempt and the figures run long. A dark sky matters more here than for any other type, and the Moon must be down.

About the ZWO Seestar S50

The scope that made smart astrophotography mainstream. 50 mm triplet, 2 MP sensor, dual-band filter on a wheel. Alt-Az stacking at 10 s, EQ mode unlocks 60 s. Out of production since 2026 and replaced by the S50 Pro, but there are a great many in use.

10, 20 and 30 s in Alt-Az; 60 s only in EQ mode (app 2.5 and later). Built-in dual-band light-pollution filter, switchable in the app.

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 S50ZWO 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 Witch Head Nebula with your Seestar S50? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Witch Head Nebula from a Seestar S50? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Witch Head Nebula · All targets for the Seestar S50