How long to image the Trifid Nebula with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 35 min (70 subs of 30 s with the built-in dual-narrowband (Hα + OIII) filter) for a solid image of the Trifid Nebula. A quick look takes 9 min; a showpiece 2 h 19 min. Under a Bortle 3 rural sky the solid figure drops to 24 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 38% of the frame’s short side.

Trifid Nebula with the DwarfLab Draco: 30 s subs with the built-in dual-narrowband (Hα + OIII) filter.
SkyQuick lookTarget obvious, still noisySolidClean enough to shareShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site6 min12 subs23 min47 subs1 h 34 min188 subs
Bortle 2Typical dark site6 min12 subs24 min48 subs1 h 35 min191 subs
Bortle 3Rural6 min13 subs24 min49 subs1 h 38 min196 subs
Bortle 4Rural / suburban transition7 min14 subs26 min53 subs1 h 44 min209 subs
Bortle 5Suburban7 min15 subs29 min58 subs1 h 54 min229 subs
Bortle 6Bright suburban9 min18 subs35 min70 subs2 h 19 min279 subs
Bortle 7Suburban / urban transition12 min24 subs47 min94 subs3 h 06 min373 subs
Bortle 8City16 min33 subs1 h 05 min130 subs4 h 20 min520 subs
Bortle 9Inner city26 min53 subs1 h 44 min209 subs6 h 56 min833 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 45 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.)

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How it frames

The Trifid Nebula is 28′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 38% 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 lengthBortle 3Bortle 5Bortle 7
30 s24 min49 subs29 min58 subs47 min94 subs
60 s30 min30 subs30 min30 subs41 min41 subs
120 s1 h30 subs1 h30 subs1 h30 subs
300 s2 h 30 min30 subs2 h 30 min30 subs2 h 30 min30 subs

With and without the dual-band filter

Solid quality, default sub length.
FilterBortle 3Bortle 5Bortle 7
No filter21 min43 subs35 min70 subs1 h 33 min187 subs
dual-narrowband (Hα + OIII)24 min49 subs29 min58 subs47 min94 subs

About the Trifid Nebula

Red emission, blue reflection and dark lanes in one object. Shoot it without a filter to keep the blue, or dual-band for the red.

M20, NGC 6514 · Emission nebula in Sagittarius · magnitude 6.3 · 28′ · best in Jun, Jul, Aug. 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 Trifid Nebula with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

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