How long to image the M4 with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 1 h 14 min (296 subs of 15 s) for a solid image of the M4. A quick look takes 18 min; a showpiece 4 h 56 min. Under a Bortle 3 rural sky the solid figure drops to 29 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 50% 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 | 6 min25 subs | 24 min98 subs | 1 h 38 min392 subs |
| Bortle 2Typical dark site | 6 min26 subs | 26 min104 subs | 1 h 44 min416 subs |
| Bortle 3Rural | 7 min29 subs | 29 min116 subs | 1 h 55 min462 subs |
| Bortle 4Rural / suburban transition | 9 min36 subs | 36 min144 subs | 2 h 23 min573 subs |
| Bortle 5Suburban | 12 min47 subs | 47 min188 subs | 3 h 07 min750 subs |
| Bortle 6Bright suburban | 18 min74 subs | 1 h 14 min296 subs | 4 h 56 min1,184 subs |
| Bortle 7Suburban / urban transition | 31 min126 subs | 2 h 06 min503 subs | 8 h 23 min2,011 subs |
| Bortle 8City | 51 min206 subs | 3 h 26 min824 subs | 14 h3,295 subs |
| Bortle 9Inner city | 1 h 34 min377 subs | 6 h 17 min1,508 subs | 25 h6,032 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 36 min of run time. The DWARF mini’s battery (rated about 3 h 30 min) 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 10000mAh 20W7,000 mAh inside, about four hours; a PD bank extends the night.
- 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 DWARF mini →
How it frames
The M4 is 36′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it fills 50% of the frame’s short side.
Longer subs
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 29 min116 subs | 47 min188 subs | 2 h 06 min503 subs |
| 30 s | 25 min50 subs | 43 min86 subs | 2 h 02 min244 subs |
| 60 s | 30 min30 subs | 41 min41 subs | 2 h120 subs |
| 90 s | 45 min30 subs | 45 min30 subs | 1 h 59 min80 subs |
Leave the dual-band filter out for the M4. 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 12 times slower.
About the M4
The loose globular next to Antares. Low in the sky from the UK, so image it near transit.
NGC 6121 · Globular cluster in Scorpius · magnitude 5.9 · 36′ · best in May, Jun, Jul. 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 DWARF mini
DwarfLab’s answer to the Seestar S30: same sensor and focal length, big pixels, dual-band filter built in, and 90 s subs in EQ mode. Sensitivity over megapixels.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 90 s is the ceiling. Built-in Astro (430 to 690 nm), dark-frame and dual-band Hα / OIII filters; no plain VIS filter on the tele camera.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 15 s and 90 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 M4 from a DWARF mini? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M4 with the ZWO Seestar S50: 1 h 14 min from Bortle 6
- M4 with the ZWO Seestar S50 Pro: 1 h 21 min from Bortle 6
- M4 with the ZWO Seestar S30: 1 h 18 min from Bortle 6
- M4 with the ZWO Seestar S30 Pro: 1 h 26 min from Bortle 6
- M4 with the DwarfLab DWARF 3: 1 h 48 min from Bortle 6
- M4 with the DwarfLab Draco: 1 h 01 min from Bortle 6
- M4 with the DwarfLab DWARF II: 4 h 14 min from Bortle 6
- M4 with the Vaonis Vespera II: 1 h 14 min from Bortle 6
- M4 with the Vaonis Vespera Pro: 2 h 46 min from Bortle 6
- M4 with the Vaonis Vespera 3: 1 h 11 min from Bortle 6
- M4 with the Vaonis Vespera Pro 2: 2 h 39 min from Bortle 6
- M4 with the Unistellar eQuinox 2: 1 h 07 min from Bortle 6
- M4 with the Unistellar Odyssey: 5 h 11 min from Bortle 6
- M4 with the Celestron Origin: 20 min from Bortle 6
- M4 with the Celestron Origin Mark II: 27 min from Bortle 6