How long should I image the Abell 39 with the Origin Mark II from a Bortle 6 sky?

About 13 h of total integration for a solid image, or 53 h for a showpiece. A quick look takes 3 h 19 min.

How many subs is that on the Origin Mark II?

At the default 10 s sub length, 4,766 subs for a solid image from Bortle 6 and 1,233 from Bortle 3.

Does a dual-band filter help on the Abell 39?

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 13 h to 5 h 14 min.

How long to image the Abell 39 with the Celestron Origin Mark II

From a Bortle 6 suburban sky, the Celestron Origin Mark II needs about 13 h (4,766 subs of 10 s) for a solid image of the Abell 39. A quick look takes 3 h 19 min; a showpiece 53 h. Under a Bortle 3 rural sky the solid figure drops to 3 h 25 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 6% of the frame’s short side.

Abell 39 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	37 min222 subs	2 h 28 min888 subs	9 h 52 min3,552 subs
Bortle 2Typical dark site	42 min252 subs	2 h 48 min1,007 subs	11 h4,028 subs
Bortle 3Rural	51 min309 subs	3 h 25 min1,233 subs	14 h4,929 subs
Bortle 4Rural / suburban transition	1 h 14 min445 subs	4 h 56 min1,778 subs	20 h7,112 subs
Bortle 5Suburban	1 h 50 min661 subs	7 h 20 min2,643 subs	29 h10,572 subs
Bortle 6Bright suburban	3 h 19 min1,192 subs	13 h4,766 subs	53 h19,061 subs
Bortle 7Suburban / urban transition	6 h 07 min2,203 subs	24 h8,809 subs	98 h35,236 subs
Bortle 8City	10 h3,772 subs	42 h15,088 subs	170+ h60,350 subs
Bortle 9Inner city	20 h7,120 subs	79 h28,478 subs	320+ h113,910 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 17 h of run time. That is more than one night: over 3 nights, about 5 h 44 min each. The Origin Mark II’s battery is rated at about 6 h, which is cutting it fine; take a power bank. (Bortle 6, solid image; we allow 30% over the integration time.)

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How it frames

The Abell 39 is 2.9′ across. The Origin Mark II frames 1.32° × 0.75° at 1.23″ per pixel, so it fills 6% 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	3 h 25 min1,233 subs	7 h 20 min2,643 subs	24 h8,809 subs
15 s	3 h 20 min800 subs	7 h 15 min1,741 subs	24 h5,851 subs
30 s	3 h 15 min390 subs	7 h 10 min860 subs	24 h2,915 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	3 h 25 min1,233 subs	7 h 20 min2,643 subs	24 h8,809 subs
dual-band (Nebula Filter), drawer	2 h 14 min806 subs	3 h 26 min1,238 subs	8 h 41 min3,125 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 Abell 39

A near-perfect faint sphere in Hercules. Very low surface brightness, an OIII target for dark skies and long dual-band stacks.

PN A66 39 · Planetary nebula in Hercules · magnitude 13.7 · 2.9′ · best in May, Jun, Jul. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.

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.

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Imaged the Abell 39 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 Abell 39 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 Abell 39 · All targets for the Origin Mark II