How long to image the M28 with the DwarfLab DWARF II
From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 20 min (82 subs of 15 s) for a solid image of the M28. A quick look takes 5 min; a showpiece 1 h 21 min. Under a Bortle 3 rural sky the solid figure drops to 13 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 10% 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 | 3 min12 subs | 12 min48 subs | 47 min189 subs |
| Bortle 2Typical dark site | 3 min13 subs | 12 min49 subs | 48 min193 subs |
| Bortle 3Rural | 3 min13 subs | 13 min51 subs | 50 min201 subs |
| Bortle 4Rural / suburban transition | 3 min14 subs | 14 min56 subs | 55 min221 subs |
| Bortle 5Suburban | 4 min16 subs | 16 min63 subs | 1 h 03 min251 subs |
| Bortle 6Bright suburban | 5 min21 subs | 20 min82 subs | 1 h 21 min326 subs |
| Bortle 7Suburban / urban transition | 7 min30 subs | 29 min118 subs | 1 h 57 min470 subs |
| Bortle 8City | 11 min44 subs | 43 min173 subs | 2 h 53 min692 subs |
| Bortle 9Inner city | 18 min73 subs | 1 h 13 min292 subs | 4 h 52 min1,167 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 26 min of run time. The DWARF II’s battery (rated about 3 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 10000mAh 18W18 W PD input; runs while charging.
- 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 II →
How it frames
The M28 is 11′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 10% of the frame’s short side.
About the M28
A compact globular near Lambda Sagittarii, a degree from M22. Small and quick.
NGC 6626 · Globular cluster in Sagittarius · magnitude 6.8 · 11′ · best in Jun, Jul, Aug. 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 II
The original pocket scope. 24 mm aperture and tiny 1.45 µm pixels mean it is slow per pixel, so bin or downsample and be patient.
15 s is the hard maximum in any mode; DwarfLab recommends EQ mode at 15 s. Two built-in filters, VIS and Astro (IR-pass); no dual-band. The optional UHC filter is no longer sold.
The DWARF II uses fixed 15 s subs, so the only levers you have are the sky you shoot from, the filter, and total time.
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 M28 from a DWARF II? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M28 with the ZWO Seestar S50: 6 min from Bortle 6
- M28 with the ZWO Seestar S50 Pro: 7 min from Bortle 6
- M28 with the ZWO Seestar S30: 7 min from Bortle 6
- M28 with the ZWO Seestar S30 Pro: 7 min from Bortle 6
- M28 with the DwarfLab DWARF 3: 9 min from Bortle 6
- M28 with the DwarfLab DWARF mini: 8 min from Bortle 6
- M28 with the DwarfLab Draco: 15 min from Bortle 6
- M28 with the Vaonis Vespera II: 6 min from Bortle 6
- M28 with the Vaonis Vespera Pro: 14 min from Bortle 6
- M28 with the Vaonis Vespera 3: 6 min from Bortle 6
- M28 with the Vaonis Vespera Pro 2: 13 min from Bortle 6
- M28 with the Unistellar eQuinox 2: 5 min from Bortle 6
- M28 with the Unistellar Odyssey: 23 min from Bortle 6
- M28 with the Celestron Origin: 5 min from Bortle 6
- M28 with the Celestron Origin Mark II: 5 min from Bortle 6