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

About 51 min of total integration for a solid image, or 3 h 22 min for a showpiece. A quick look takes 13 min.

How many subs is that on the Seestar S30?

At the default 10 s sub length, 304 subs for a solid image from Bortle 6 and 230 from Bortle 3.

Does a dual-band filter help on the Trifid Nebula?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 1 h 10 min to 51 min.

How long to image the Trifid Nebula with the ZWO Seestar S30

From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 51 min (304 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Trifid Nebula. A quick look takes 13 min; a showpiece 3 h 22 min. Under a Bortle 3 rural sky the solid figure drops to 38 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 39% of the frame’s short side.

Trifid Nebula with the ZWO Seestar S30: 10 s subs with the built-in dual-band (LP filter) filter.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	9 min56 subs	37 min222 subs	2 h 28 min888 subs
Bortle 2Typical dark site	9 min57 subs	37 min225 subs	2 h 30 min898 subs
Bortle 3Rural	10 min58 subs	38 min230 subs	2 h 33 min917 subs
Bortle 4Rural / suburban transition	10 min61 subs	40 min241 subs	2 h 40 min963 subs
Bortle 5Suburban	11 min65 subs	43 min259 subs	2 h 53 min1,036 subs
Bortle 6Bright suburban	13 min76 subs	51 min304 subs	3 h 22 min1,214 subs
Bortle 7Suburban / urban transition	16 min98 subs	1 h 05 min389 subs	4 h 19 min1,554 subs
Bortle 8City	22 min131 subs	1 h 27 min521 subs	5 h 47 min2,082 subs
Bortle 9Inner city	33 min201 subs	2 h 14 min802 subs	8 h 54 min3,207 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 1 h 06 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.
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Seestar S30 dew shieldHeater is built in; a cheap shield reduces dew and stray light.
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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 Trifid Nebula is 28′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 39% 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	38 min230 subs	43 min259 subs	1 h 05 min389 subs
20 s	27 min82 subs	32 min97 subs	54 min161 subs
30 s	23 min47 subs	28 min57 subs	50 min100 subs
60 s	30 min30 subs	30 min30 subs	46 min47 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
UV/IR-cut (no light-pollution filter)	30 min179 subs	46 min276 subs	1 h 56 min699 subs
dual-band (LP filter)	38 min230 subs	43 min259 subs	1 h 05 min389 subs

About the Trifid Nebula

Red emission, blue reflection and dark lanes in one object. Shoot it without a filter to keep the blue, or dual-band for the red.

M20, NGC 6514 · Emission nebula in Sagittarius · magnitude 6.3 · 28′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Emission nebulae glow in a few narrow lines, mostly hydrogen-alpha (deep red) and doubly ionised oxygen (teal). A dual-band filter passes those lines and blocks most skyglow, which is why it cuts the time needed from a suburban sky so dramatically. Use it. From a genuinely dark site the gain is smaller because there is less skyglow to block, and read noise becomes the limit, which is where longer subs (EQ mode, or Expert Mode on a Vespera) earn their keep.

Stars lose colour through a dual-band filter; a short broadband stack blended in fixes that if you care.

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 Trifid Nebula with your Seestar S30? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Trifid Nebula 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 Trifid Nebula · All targets for the Seestar S30