How long to image the M75 with the DwarfLab DWARF II
From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 1 h 02 min (250 subs of 15 s) for a solid image of the M75. A quick look takes 16 min; a showpiece 4 h 10 min. Under a Bortle 3 rural sky the solid figure drops to 36 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 6% 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 | 8 min34 subs | 34 min135 subs | 2 h 15 min540 subs |
| Bortle 2Typical dark site | 9 min35 subs | 35 min139 subs | 2 h 18 min554 subs |
| Bortle 3Rural | 9 min37 subs | 36 min145 subs | 2 h 25 min580 subs |
| Bortle 4Rural / suburban transition | 10 min41 subs | 40 min162 subs | 2 h 41 min645 subs |
| Bortle 5Suburban | 12 min47 subs | 47 min187 subs | 3 h 07 min748 subs |
| Bortle 6Bright suburban | 16 min63 subs | 1 h 02 min250 subs | 4 h 10 min999 subs |
| Bortle 7Suburban / urban transition | 23 min93 subs | 1 h 32 min370 subs | 6 h 09 min1,478 subs |
| Bortle 8City | 35 min139 subs | 2 h 19 min556 subs | 9 h 16 min2,223 subs |
| Bortle 9Inner city | 1 h239 subs | 3 h 58 min953 subs | 16 h3,810 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 21 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 M75 is 6′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 6% of the frame’s short side.
About the M75
A remote, tightly packed globular. Small and faint, but its dense core shows up fast.
NGC 6864 · Globular cluster in Sagittarius · magnitude 8.5 · 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 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 M75 from a DWARF II? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M75 with the ZWO Seestar S50: 19 min from Bortle 6
- M75 with the ZWO Seestar S50 Pro: 21 min from Bortle 6
- M75 with the ZWO Seestar S30: 20 min from Bortle 6
- M75 with the ZWO Seestar S30 Pro: 22 min from Bortle 6
- M75 with the DwarfLab DWARF 3: 28 min from Bortle 6
- M75 with the DwarfLab DWARF mini: 19 min from Bortle 6
- M75 with the DwarfLab Draco: 16 min from Bortle 6
- M75 with the Vaonis Vespera II: 19 min from Bortle 6
- M75 with the Vaonis Vespera Pro: 42 min from Bortle 6
- M75 with the Vaonis Vespera 3: 18 min from Bortle 6
- M75 with the Vaonis Vespera Pro 2: 40 min from Bortle 6
- M75 with the Unistellar eQuinox 2: 16 min from Bortle 6
- M75 with the Unistellar Odyssey: 1 h 13 min from Bortle 6
- M75 with the Celestron Origin: 5 min from Bortle 6
- M75 with the Celestron Origin Mark II: 7 min from Bortle 6