How long should I image the De Mairan's Nebula with the Seestar S30 Pro from a Bortle 6 sky?

About 38 min of total integration for a solid image, or 2 h 32 min for a showpiece. A quick look takes 10 min.

How many subs is that on the Seestar S30 Pro?

At the default 10 s sub length, 229 subs for a solid image from Bortle 6 and 170 from Bortle 3.

Does a dual-band filter help on the De Mairan's Nebula?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 55 min to 38 min.

How long to image the De Mairan's Nebula with the ZWO Seestar S30 Pro

From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 38 min (229 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the De Mairan's Nebula. A quick look takes 10 min; a showpiece 2 h 32 min. Under a Bortle 3 rural sky the solid figure drops to 28 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 15% of the frame’s short side.

De Mairan's Nebula with the ZWO Seestar S30 Pro: 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	7 min41 subs	27 min164 subs	1 h 49 min656 subs
Bortle 2Typical dark site	7 min42 subs	28 min166 subs	1 h 51 min664 subs
Bortle 3Rural	7 min43 subs	28 min170 subs	1 h 53 min679 subs
Bortle 4Rural / suburban transition	7 min45 subs	30 min179 subs	1 h 59 min715 subs
Bortle 5Suburban	8 min49 subs	32 min193 subs	2 h 09 min772 subs
Bortle 6Bright suburban	10 min58 subs	38 min229 subs	2 h 32 min913 subs
Bortle 7Suburban / urban transition	12 min74 subs	49 min295 subs	3 h 17 min1,180 subs
Bortle 8City	17 min100 subs	1 h 06 min399 subs	4 h 26 min1,596 subs
Bortle 9Inner city	26 min156 subs	1 h 43 min621 subs	6 h 54 min2,482 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 49 min of run time. The Seestar S30 Pro’s battery (rated about 5 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, 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.
Amazon UK Amazon US
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.
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 S30 Pro →

How it frames

The De Mairan's Nebula is 20′ × 15′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it fills 15% 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	28 min170 subs	32 min193 subs	49 min295 subs
20 s	21 min65 subs	25 min76 subs	42 min127 subs
30 s	19 min39 subs	23 min46 subs	40 min80 subs
60 s	30 min30 subs	30 min30 subs	38 min38 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)	23 min138 subs	36 min214 subs	1 h 31 min547 subs
dual-band (LP filter)	28 min170 subs	32 min193 subs	49 min295 subs

About the De Mairan's Nebula

The comma-shaped nebula north of the Orion Nebula's core, split from it by a dark lane. Always in the same frame as M42.

M43, NGC 1982 · Emission nebula in Orion · magnitude 9.0 · 20′ × 15′ · best in Nov, Dec, Jan. 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 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 De Mairan's 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 De Mairan's 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 De Mairan's Nebula · All targets for the Seestar S30 Pro