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

About 21 min of total integration for a solid image, or 1 h 25 min for a showpiece. A quick look takes 5 min.

How many subs is that on the Origin Mark II?

At the default 10 s sub length, 129 subs for a solid image from Bortle 6 and 44 from Bortle 3.

Does a dual-band filter help on the Whirlpool Galaxy?

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

How long to image the Whirlpool Galaxy with the Celestron Origin Mark II

From a Bortle 6 suburban sky, the Celestron Origin Mark II needs about 21 min (129 subs of 10 s) for a solid image of the Whirlpool Galaxy. A quick look takes 5 min; a showpiece 1 h 25 min. Under a Bortle 3 rural sky the solid figure drops to 7 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 25% of the frame’s short side.

Whirlpool Galaxy 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	2 min10 subs	6 min36 subs	24 min142 subs
Bortle 2Typical dark site	2 min10 subs	6 min39 subs	26 min154 subs
Bortle 3Rural	2 min11 subs	7 min44 subs	29 min175 subs
Bortle 4Rural / suburban transition	2 min15 subs	9 min57 subs	38 min227 subs
Bortle 5Suburban	3 min20 subs	13 min78 subs	52 min310 subs
Bortle 6Bright suburban	5 min33 subs	21 min129 subs	1 h 25 min513 subs
Bortle 7Suburban / urban transition	9 min57 subs	37 min225 subs	2 h 30 min899 subs
Bortle 8City	16 min94 subs	1 h 02 min375 subs	4 h 10 min1,500 subs
Bortle 9Inner city	29 min174 subs	1 h 56 min695 subs	7 h 43 min2,779 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 28 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 Whirlpool Galaxy is 11′ × 7′ across. The Origin Mark II frames 1.32° × 0.75° at 1.23″ per pixel, so it fills 25% 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	7 min44 subs	13 min78 subs	37 min225 subs
15 s	8 min30 subs	13 min52 subs	37 min150 subs
30 s	15 min30 subs	15 min30 subs	37 min75 subs

About the Whirlpool Galaxy

The classic face-on spiral with its companion tugging at one arm. Small in a smart scope but bright; the arms appear within an hour, the tidal bridge needs several.

M51, NGC 5194 · Galaxy in Canes Venatici · magnitude 8.4 · 11′ × 7′ · best in Mar, Apr, May. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.

Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.

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 Whirlpool Galaxy 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 Whirlpool Galaxy 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 Whirlpool Galaxy · All targets for the Origin Mark II