How long to image the M5 with the DwarfLab Draco

From a Bortle 6 suburban sky, the DwarfLab Draco needs about 15 min (30 subs of 30 s) for a solid image of the M5. A quick look takes 5 min; a showpiece 45 min. Under a Bortle 3 rural sky the solid figure drops to 15 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 31% of the frame’s short side.

M5 with the DwarfLab Draco: 30 s subs.
SkyQuick lookTarget obvious, still noisySolidClean enough to shareShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site5 min10 subs15 min30 subs45 min90 subs
Bortle 2Typical dark site5 min10 subs15 min30 subs45 min90 subs
Bortle 3Rural5 min10 subs15 min30 subs45 min90 subs
Bortle 4Rural / suburban transition5 min10 subs15 min30 subs45 min90 subs
Bortle 5Suburban5 min10 subs15 min30 subs45 min90 subs
Bortle 6Bright suburban5 min10 subs15 min30 subs45 min90 subs
Bortle 7Suburban / urban transition5 min10 subs15 min30 subs53 min107 subs
Bortle 8City5 min11 subs21 min43 subs1 h 24 min169 subs
Bortle 9Inner city9 min19 subs37 min75 subs2 h 30 min300 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 20 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 M5 is 23′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 31% 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 s15 min30 subs15 min30 subs15 min30 subs
60 s30 min30 subs30 min30 subs30 min30 subs
120 s1 h30 subs1 h30 subs1 h30 subs
300 s2 h 30 min30 subs2 h 30 min30 subs2 h 30 min30 subs

Leave the dual-band filter out for the M5. It is a globular cluster, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 6 times slower.

About the M5

A bright, slightly elliptical globular in Serpens that rivals M13 and resolves into stars quickly.

NGC 5904 · Globular cluster in Serpens · magnitude 5.7 · 23′ · best in Apr, May, Jun. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.

Globular clusters are point sources packed tight, so they come quickly: the core resolves into stars within a handful of minutes on any smart scope. More time deepens the halo and pulls in the faint outer members. Use short subs so the core does not saturate into a white blob, and no filter.

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 M5 with your Draco? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the M5 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 M5 · All targets for the Draco