How long to image the M21 with the DwarfLab DWARF II
From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 9 min (38 subs of 15 s) for a solid image of the M21. A quick look takes 3 min; a showpiece 38 min. Under a Bortle 3 rural sky the solid figure drops to 8 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 12% 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 min10 subs | 8 min30 subs | 24 min95 subs |
| Bortle 2Typical dark site | 3 min10 subs | 8 min30 subs | 24 min97 subs |
| Bortle 3Rural | 3 min10 subs | 8 min30 subs | 25 min100 subs |
| Bortle 4Rural / suburban transition | 3 min10 subs | 8 min30 subs | 27 min108 subs |
| Bortle 5Suburban | 3 min10 subs | 8 min31 subs | 30 min121 subs |
| Bortle 6Bright suburban | 3 min10 subs | 9 min38 subs | 38 min152 subs |
| Bortle 7Suburban / urban transition | 3 min14 subs | 13 min53 subs | 53 min212 subs |
| Bortle 8City | 5 min20 subs | 19 min77 subs | 1 h 16 min305 subs |
| Bortle 9Inner city | 8 min32 subs | 31 min126 subs | 2 h 05 min502 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 12 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 M21 is 13′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 12% of the frame’s short side.
About the M21
A young open cluster beside the Trifid Nebula. Comes for free in a Trifid frame.
NGC 6531 · Open cluster in Sagittarius · magnitude 5.9 · 13′ · best in Jun, Jul, Aug. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Open clusters are the easiest targets in the sky. The stars are bright, so the aim is colour and tight stars rather than depth: short subs, no filter, and stop before the bright members saturate. The nominal time here gets you clean star colour; more integration only adds background stars.
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 M21 from a DWARF II? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M21 with the ZWO Seestar S50: 5 min from Bortle 6
- M21 with the ZWO Seestar S50 Pro: 5 min from Bortle 6
- M21 with the ZWO Seestar S30: 5 min from Bortle 6
- M21 with the ZWO Seestar S30 Pro: 5 min from Bortle 6
- M21 with the DwarfLab DWARF 3: 8 min from Bortle 6
- M21 with the DwarfLab DWARF mini: 8 min from Bortle 6
- M21 with the DwarfLab Draco: 15 min from Bortle 6
- M21 with the Vaonis Vespera II: 5 min from Bortle 6
- M21 with the Vaonis Vespera Pro: 7 min from Bortle 6
- M21 with the Vaonis Vespera 3: 5 min from Bortle 6
- M21 with the Vaonis Vespera Pro 2: 6 min from Bortle 6
- M21 with the Unistellar eQuinox 2: 2 min from Bortle 6
- M21 with the Unistellar Odyssey: 10 min from Bortle 6
- M21 with the Celestron Origin: 5 min from Bortle 6
- M21 with the Celestron Origin Mark II: 5 min from Bortle 6