How long should I image the Witch Head Nebula with the Seestar S30 Pro from a Bortle 6 sky?

About 47 h of total integration for a solid image, or 190+ h for a showpiece. A quick look takes 12 h.

How many subs is that on the Seestar S30 Pro?

At the default 10 s sub length, 16,983 subs for a solid image from Bortle 6 and 5,998 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 S30 Pro

From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 47 h (16,983 subs of 10 s) for a solid image of the Witch Head Nebula. A quick look takes 12 h; a showpiece 190+ h. Under a Bortle 3 rural sky the solid figure drops to 17 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 just over the frame at 1.3×.

Witch Head Nebula 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	3 h 25 min1,232 subs	14 h4,927 subs	55 h19,707 subs
Bortle 2Typical dark site	3 h 41 min1,325 subs	15 h5,297 subs	59 h21,188 subs
Bortle 3Rural	4 h 10 min1,500 subs	17 h5,998 subs	67 h23,990 subs
Bortle 4Rural / suburban transition	5 h 21 min1,924 subs	21 h7,695 subs	85 h30,777 subs
Bortle 5Suburban	7 h 13 min2,596 subs	29 h10,384 subs	120+ h41,535 subs
Bortle 6Bright suburban	12 h4,246 subs	47 h16,983 subs	190+ h67,930 subs
Bortle 7Suburban / urban transition	21 h7,390 subs	82 h29,557 subs	330+ h118,225 subs
Bortle 8City	34 h12,270 subs	140+ h49,079 subs	550+ h196,315 subs
Bortle 9Inner city	63 h22,679 subs	250+ h90,714 subs	1010+ h362,856 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 61 h of run time. That is more than one night: over 9 nights, about 6 h 49 min each. The Seestar S30 Pro’s battery is rated at about 5 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 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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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.
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How it frames

The Witch Head Nebula is 180′ × 60′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it is just over the frame at 1.3×. Point at the part you want; the edges will fall outside the frame.

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	17 h5,998 subs	29 h10,384 subs	82 h29,557 subs
20 s	13 h2,415 subs	26 h4,608 subs	79 h14,194 subs
30 s	12 h1,480 subs	25 h2,942 subs	78 h9,333 subs
60 s	11 h675 subs	23 h1,406 subs	77 h4,602 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 13 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 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 Witch Head Nebula 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 Witch Head Nebula 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 Witch Head Nebula · All targets for the Seestar S30 Pro