How long should I image the Crescent Nebula with the Origin Mark II from a Bortle 6 sky?

About 1 h 40 min of total integration for a solid image, or 6 h 40 min for a showpiece. A quick look takes 25 min.

How many subs is that on the Origin Mark II?

At the default 10 s sub length, 600 subs for a solid image from Bortle 6 and 168 from Bortle 3.

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

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 1 h 40 min to 42 min.

How long to image the Crescent Nebula with the Celestron Origin Mark II

From a Bortle 6 suburban sky, the Celestron Origin Mark II needs about 1 h 40 min (600 subs of 10 s) for a solid image of the Crescent Nebula. A quick look takes 25 min; a showpiece 6 h 40 min. Under a Bortle 3 rural sky the solid figure drops to 28 min. 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 fills 40% of the frame’s short side.

Crescent Nebula with the Celestron Origin Mark II: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	5 min32 subs	21 min126 subs	1 h 23 min501 subs
Bortle 2Typical dark site	6 min35 subs	23 min140 subs	1 h 33 min559 subs
Bortle 3Rural	7 min42 subs	28 min168 subs	1 h 51 min669 subs
Bortle 4Rural / suburban transition	10 min59 subs	39 min235 subs	2 h 36 min937 subs
Bortle 5Suburban	14 min85 subs	57 min340 subs	3 h 47 min1,360 subs
Bortle 6Bright suburban	25 min150 subs	1 h 40 min600 subs	6 h 40 min2,399 subs
Bortle 7Suburban / urban transition	46 min274 subs	3 h 02 min1,095 subs	12 h4,379 subs
Bortle 8City	1 h 18 min466 subs	5 h 11 min1,864 subs	21 h7,453 subs
Bortle 9Inner city	2 h 26 min876 subs	9 h 44 min3,503 subs	39 h14,010 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 10 min of run time. The Origin Mark II’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.)

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How it frames

The Crescent Nebula is 18′ × 12′ across. The Origin Mark II frames 1.32° × 0.75° at 1.23″ per pixel, so it fills 40% of the frame’s short side.

Longer subs

10 s auto subs (15 s with the Nebula Filter); manual 1 to 30 s on the alt-az mount, longer only with the EQ wedge, and 60 s and up needs the StarSense Autoguider too. Celestron warns the f/2.2 optics saturate quickly without the filter. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	28 min168 subs	57 min340 subs	3 h 02 min1,095 subs
15 s	27 min109 subs	56 min224 subs	3 h 02 min728 subs
30 s	27 min54 subs	55 min111 subs	3 h 01 min363 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	28 min168 subs	57 min340 subs	3 h 02 min1,095 subs
dual-band (Nebula Filter), drawer	20 min123 subs	29 min175 subs	1 h 08 min406 subs

The Origin Mark II has no built-in dual-band filter. Filter drawer takes 1.25-inch or 2-inch filters, including dual-band; Celestron sells an optional Nebula Filter. On an emission target like this it is the single biggest upgrade you can make.

About the Crescent Nebula

A shell blown by a Wolf-Rayet star, bright in H-alpha with a faint OIII skin. Small, so the bigger scopes do it justice.

NGC 6888, Caldwell 27 · Emission nebula in Cygnus · magnitude 7.4 · 18′ × 12′ · 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 Celestron Origin Mark II

The Origin Mark II (late 2025): the same 6-inch f/2.2 RASA with an 8 MP IMX678 in place of the original 6 MP IMX178. Smaller pixels for finer detail, a quieter sensor, and still the fastest system here by a wide margin.

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 30 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 Origin Mark IICelestron store Direct Amazon UK Amazon USThe Celestron 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 Crescent Nebula with your Origin Mark II? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Crescent Nebula from a Origin Mark II? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Crescent Nebula · All targets for the Origin Mark II