How long should I image the Elephant's Trunk Nebula with the Seestar S30 from a Bortle 6 sky?

About 2 h 47 min of total integration for a solid image, or 11 h for a showpiece. A quick look takes 42 min.

How many subs is that on the Seestar S30?

At the default 10 s sub length, 1,003 subs for a solid image from Bortle 6 and 733 from Bortle 3.

Does a dual-band filter help on the Elephant's Trunk Nebula?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 4 h 03 min to 2 h 47 min.

How long to image the Elephant's Trunk Nebula with the ZWO Seestar S30

From a Bortle 6 suburban sky, the ZWO Seestar S30 needs about 2 h 47 min (1,003 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Elephant's Trunk Nebula. A quick look takes 42 min; a showpiece 11 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 02 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is 2.4× wider than the frame.

Elephant's Trunk 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	29 min177 subs	1 h 58 min707 subs	7 h 51 min2,826 subs
Bortle 2Typical dark site	30 min179 subs	1 h 59 min716 subs	7 h 57 min2,862 subs
Bortle 3Rural	31 min184 subs	2 h 02 min733 subs	8 h 08 min2,931 subs
Bortle 4Rural / suburban transition	32 min194 subs	2 h 09 min775 subs	8 h 36 min3,097 subs
Bortle 5Suburban	35 min211 subs	2 h 20 min841 subs	9 h 20 min3,361 subs
Bortle 6Bright suburban	42 min251 subs	2 h 47 min1,003 subs	11 h4,009 subs
Bortle 7Suburban / urban transition	55 min328 subs	3 h 38 min1,311 subs	15 h5,243 subs
Bortle 8City	1 h 15 min448 subs	4 h 58 min1,790 subs	20 h7,159 subs
Bortle 9Inner city	1 h 57 min703 subs	7 h 49 min2,812 subs	31 h11,246 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 3 h 37 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 Elephant's Trunk Nebula is 170′ × 140′ across. The Seestar S30 frames 2.13° × 1.20° at 3.99″ per pixel, so it is 2.4× 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, which needs the TH10 head. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	2 h 02 min733 subs	2 h 20 min841 subs	3 h 38 min1,311 subs
20 s	1 h 22 min246 subs	1 h 40 min300 subs	2 h 58 min535 subs
30 s	1 h 08 min137 subs	1 h 26 min173 subs	2 h 45 min330 subs
60 s	55 min55 subs	1 h 13 min73 subs	2 h 31 min152 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)	1 h 37 min580 subs	2 h 35 min932 subs	6 h 51 min2,469 subs
dual-band (LP filter)	2 h 02 min733 subs	2 h 20 min841 subs	3 h 38 min1,311 subs

About the Elephant's Trunk Nebula

A vast, faint hydrogen cloud in Cepheus with the dark trunk winding through it. Huge, so wide scopes frame the whole thing; dual-band is essential from any lit sky.

IC 1396 · Emission nebula in Cepheus · magnitude 3.5 · 170′ × 140′ · best in Jul, Aug, Sep. 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.

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Imaged the Elephant's Trunk 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 Elephant's Trunk Nebula from a Seestar S30? Email it with your total time and sky to [email protected] and it goes here, credited.

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