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

About 2 h 21 min of total integration for a solid image, or 9 h 22 min for a showpiece. A quick look takes 35 min.

How many subs is that on the Draco?

At the default 30 s sub length, 282 subs for a solid image from Bortle 6 and 188 from Bortle 3.

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

Yes. It is an emission-line object; from Bortle 6 the filter cuts the solid-image time from 3 h 57 min to 2 h 21 min.

How long to image the Cocoon Nebula with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 2 h 21 min (282 subs of 30 s with the built-in dual-narrowband (Hα + OIII) filter) for a solid image of the Cocoon Nebula. A quick look takes 35 min; a showpiece 9 h 22 min. Under a Bortle 3 rural sky the solid figure drops to 1 h 34 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 16% of the frame’s short side.

Cocoon 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	22 min45 subs	1 h 29 min179 subs	5 h 57 min714 subs
Bortle 2Typical dark site	23 min46 subs	1 h 31 min182 subs	6 h 03 min727 subs
Bortle 3Rural	23 min47 subs	1 h 34 min188 subs	6 h 15 min750 subs
Bortle 4Rural / suburban transition	25 min51 subs	1 h 41 min202 subs	6 h 44 min808 subs
Bortle 5Suburban	28 min57 subs	1 h 52 min225 subs	7 h 30 min900 subs
Bortle 6Bright suburban	35 min71 subs	2 h 21 min282 subs	9 h 22 min1,125 subs
Bortle 7Suburban / urban transition	49 min98 subs	3 h 14 min389 subs	13 h1,554 subs
Bortle 8City	1 h 09 min139 subs	4 h 37 min555 subs	18 h2,219 subs
Bortle 9Inner city	1 h 54 min228 subs	7 h 35 min910 subs	30 h3,638 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 3 h 03 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 Cocoon Nebula is 12′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 16% 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 34 min188 subs	1 h 52 min225 subs	3 h 14 min389 subs
60 s	1 h 07 min68 subs	1 h 26 min87 subs	2 h 48 min168 subs
120 s	1 h30 subs	1 h 13 min37 subs	2 h 35 min78 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 24 min169 subs	2 h 25 min291 subs	6 h 52 min825 subs
dual-narrowband (Hα + OIII)	1 h 34 min188 subs	1 h 52 min225 subs	3 h 14 min389 subs

About the Cocoon Nebula

A round emission and reflection nebula at the end of a long dark lane. Mixed light, so a broadband stack keeps the blue.

IC 5146, Caldwell 19 · Emission nebula in Cygnus · magnitude 7.2 · 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 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 Cocoon Nebula with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Cocoon 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 Cocoon Nebula · All targets for the Draco