How long should I image the Bubble Nebula with the Draco from a Bortle 6 sky?

About 2 h 14 min of total integration for a solid image, or 8 h 54 min for a showpiece. A quick look takes 33 min.

How many subs is that on the Draco?

At the default 30 s sub length, 268 subs for a solid image from Bortle 6 and 178 from Bortle 3.

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

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 3 h 47 min to 2 h 14 min.

How long to image the Bubble Nebula with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 2 h 14 min (268 subs of 30 s with the built-in dual-narrowband (Hα + OIII) filter) for a solid image of the Bubble Nebula. A quick look takes 33 min; a showpiece 8 h 54 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 29 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 20% of the frame’s short side.

Bubble Nebula with the DwarfLab Draco: 30 s subs with the built-in dual-narrowband (Hα + OIII) filter.
Sky	Quick lookTarget obvious, still noisy	SolidClean enough to share	ShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site	21 min43 subs	1 h 24 min169 subs	5 h 37 min674 subs
Bortle 2Typical dark site	21 min43 subs	1 h 26 min172 subs	5 h 43 min686 subs
Bortle 3Rural	22 min45 subs	1 h 29 min178 subs	5 h 54 min709 subs
Bortle 4Rural / suburban transition	24 min48 subs	1 h 36 min192 subs	6 h 22 min765 subs
Bortle 5Suburban	27 min54 subs	1 h 47 min214 subs	7 h 06 min853 subs
Bortle 6Bright suburban	33 min67 subs	2 h 14 min268 subs	8 h 54 min1,069 subs
Bortle 7Suburban / urban transition	46 min93 subs	3 h 05 min371 subs	12 h1,481 subs
Bortle 8City	1 h 06 min133 subs	4 h 25 min531 subs	18 h2,121 subs
Bortle 9Inner city	1 h 49 min218 subs	7 h 16 min872 subs	29 h3,486 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 2 h 54 min of run time. The Draco’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.)

USB-C PD power bank 20000mAhRated 5 h on its 10,000 mAh battery. DwarfLab has not published the charging input, so check PD support before relying on it mid-session.
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How it frames

The Bubble Nebula is 15′ × 8′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 20% of the frame’s short side.

Longer subs

Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Time for a solid image by sub length:

Sub length	Bortle 3	Bortle 5	Bortle 7
30 s	1 h 29 min178 subs	1 h 47 min214 subs	3 h 05 min371 subs
60 s	1 h 03 min64 subs	1 h 21 min82 subs	2 h 40 min160 subs
120 s	1 h30 subs	1 h 09 min35 subs	2 h 27 min74 subs
300 s	2 h 30 min30 subs	2 h 30 min30 subs	2 h 30 min30 subs

With and without the dual-band filter

Solid quality, default sub length.
Filter	Bortle 3	Bortle 5	Bortle 7
No filter	1 h 20 min160 subs	2 h 19 min278 subs	6 h 35 min791 subs
dual-narrowband (Hα + OIII)	1 h 29 min178 subs	1 h 47 min214 subs	3 h 05 min371 subs

About the Bubble Nebula

A wind-blown bubble in a larger hydrogen cloud beside M52. Small; the bubble itself needs a scope with reach.

NGC 7635, Caldwell 11 · Emission nebula in Cassiopeia · magnitude 10.0 · 15′ × 8′ · best in Aug, Sep, Oct. 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 DwarfLab Draco

DwarfLab’s big scope: 90 mm of folded f/3.8 optics, the most aperture of any Seestar or DWARF, a narrow 13 nm dual-band filter and 300 s subs with built-in guiding. A small-target scope; big nebulae need its mosaic mode.

Auto Mode picks the exposure; Pro Mode allows up to 300 s, held by built-in guiding and field derotation. The 30 s default here is our assumption. Built-in Hα + OIII dual-narrowband filter, 13 nm per line; the SHO Edition adds an SII option.

Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 30 s and 300 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 Bubble Nebula with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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

Same target, other telescopes

All telescopes for the Bubble Nebula · All targets for the Draco