How long to image the M72 with the DwarfLab Draco
From a Bortle 6 suburban sky, the DwarfLab Draco needs about 59 min (118 subs of 30 s) for a solid image of the M72. A quick look takes 15 min; a showpiece 3 h 55 min. Under a Bortle 3 rural sky the solid figure drops to 24 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 8% of the frame’s short side.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 5 min11 subs | 21 min43 subs | 1 h 24 min169 subs |
| Bortle 2Typical dark site | 6 min12 subs | 22 min45 subs | 1 h 29 min178 subs |
| Bortle 3Rural | 6 min13 subs | 24 min49 subs | 1 h 38 min196 subs |
| Bortle 4Rural / suburban transition | 7 min15 subs | 30 min60 subs | 1 h 59 min238 subs |
| Bortle 5Suburban | 10 min20 subs | 38 min77 subs | 2 h 32 min305 subs |
| Bortle 6Bright suburban | 15 min30 subs | 59 min118 subs | 3 h 55 min470 subs |
| Bortle 7Suburban / urban transition | 24 min49 subs | 1 h 38 min196 subs | 6 h 32 min784 subs |
| Bortle 8City | 40 min80 subs | 2 h 39 min318 subs | 11 h1,271 subs |
| Bortle 9Inner city | 1 h 12 min145 subs | 4 h 49 min578 subs | 19 h2,311 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 16 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.
- red LED head torchRed light keeps your night vision; white light costs you twenty minutes of dark adaptation every time.
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Everything that fits the Draco →
How it frames
The M72 is 6′ across. The Draco frames 1.66° × 1.24° at 1.46″ per pixel, so it fills 8% 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 | 24 min49 subs | 38 min77 subs | 1 h 38 min196 subs |
| 60 s | 30 min30 subs | 35 min36 subs | 1 h 35 min96 subs |
| 120 s | 1 h30 subs | 1 h30 subs | 1 h 34 min47 subs |
| 300 s | 2 h 30 min30 subs | 2 h 30 min30 subs | 2 h 30 min30 subs |
Leave the dual-band filter out for the M72. 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 11 times slower.
About the M72
A faint, distant globular in Aquarius. Among the harder Messier globulars.
NGC 6981 · Globular cluster in Aquarius · magnitude 9.3 · 6′ · best in Jul, Aug, Sep. 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.
Have an image of the M72 from a Draco? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M72 with the ZWO Seestar S50: 1 h 11 min from Bortle 6
- M72 with the ZWO Seestar S50 Pro: 1 h 18 min from Bortle 6
- M72 with the ZWO Seestar S30: 1 h 15 min from Bortle 6
- M72 with the ZWO Seestar S30 Pro: 1 h 23 min from Bortle 6
- M72 with the DwarfLab DWARF 3: 1 h 44 min from Bortle 6
- M72 with the DwarfLab DWARF mini: 1 h 11 min from Bortle 6
- M72 with the DwarfLab DWARF II: 4 h 02 min from Bortle 6
- M72 with the Vaonis Vespera II: 1 h 11 min from Bortle 6
- M72 with the Vaonis Vespera Pro: 2 h 39 min from Bortle 6
- M72 with the Vaonis Vespera 3: 1 h 08 min from Bortle 6
- M72 with the Vaonis Vespera Pro 2: 2 h 32 min from Bortle 6
- M72 with the Unistellar eQuinox 2: 1 h 04 min from Bortle 6
- M72 with the Unistellar Odyssey: 4 h 51 min from Bortle 6
- M72 with the Celestron Origin: 19 min from Bortle 6
- M72 with the Celestron Origin Mark II: 26 min from Bortle 6