How long should I image the Iris Nebula with the Origin from a Bortle 6 sky?

About 30 min of total integration for a solid image, or 2 h for a showpiece. A quick look takes 7 min.

How many subs is that on the Origin?

At the default 10 s sub length, 180 subs for a solid image from Bortle 6 and 61 from Bortle 3.

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

No. The Iris Nebula is a broadband target and a dual-band filter blocks most of its light. Shoot without a filter.

How long to image the Iris Nebula with the Celestron Origin

From a Bortle 6 suburban sky, the Celestron Origin needs about 30 min (180 subs of 10 s) for a solid image of the Iris Nebula. A quick look takes 7 min; a showpiece 2 h. Under a Bortle 3 rural sky the solid figure drops to 10 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 35% of the frame’s short side.

Iris Nebula with the Celestron Origin: 10 s subs.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	2 min13 subs	8 min49 subs	32 min195 subs
Bortle 2Typical dark site	2 min14 subs	9 min53 subs	35 min212 subs
Bortle 3Rural	3 min16 subs	10 min61 subs	40 min242 subs
Bortle 4Rural / suburban transition	3 min20 subs	13 min79 subs	53 min316 subs
Bortle 5Suburban	5 min28 subs	18 min109 subs	1 h 12 min433 subs
Bortle 6Bright suburban	7 min45 subs	30 min180 subs	2 h720 subs
Bortle 7Suburban / urban transition	13 min80 subs	53 min317 subs	3 h 31 min1,268 subs
Bortle 8City	22 min133 subs	1 h 28 min530 subs	5 h 53 min2,118 subs
Bortle 9Inner city	41 min246 subs	2 h 44 min983 subs	11 h3,930 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 39 min of run time. The Origin’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 Iris Nebula is 18′ across. The Origin frames 1.27° × 0.85° at 1.48″ per pixel, so it fills 35% 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. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
10 s	10 min61 subs	18 min109 subs	53 min317 subs
15 s	9 min38 subs	17 min70 subs	52 min209 subs
30 s	15 min30 subs	17 min34 subs	51 min103 subs

About the Iris Nebula

A blue reflection nebula wrapped in dark dust. No filter helps, and the surrounding dust needs a dark sky and hours.

NGC 7023, Caldwell 4 · Reflection nebula in Cepheus · magnitude 6.8 · 18′ · best in Jul, Aug, Sep. 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 Celestron Origin

The first-generation Origin: a 6-inch f/2.2 RASA in a smart package and the fastest system here by a wide margin. Superseded by the Mark II in late 2025 and no longer sold new; Celestron offers a camera upgrade to the Mark II sensor.

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. Filter drawer takes 1.25-inch or 2-inch filters, including dual-band; Celestron sells an optional Nebula Filter.

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.

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Imaged the Iris Nebula with your Origin? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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

Same target, other telescopes

All telescopes for the Iris Nebula · All targets for the Origin