How long to image the M9 with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 49 min (198 subs of 15 s) for a solid image of the M9. A quick look takes 12 min; a showpiece 3 h 17 min. Under a Bortle 3 rural sky the solid figure drops to 20 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 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 | 4 min17 subs | 17 min67 subs | 1 h 07 min268 subs |
| Bortle 2Typical dark site | 4 min18 subs | 18 min71 subs | 1 h 11 min284 subs |
| Bortle 3Rural | 5 min20 subs | 20 min79 subs | 1 h 18 min314 subs |
| Bortle 4Rural / suburban transition | 6 min25 subs | 24 min97 subs | 1 h 37 min388 subs |
| Bortle 5Suburban | 8 min32 subs | 31 min126 subs | 2 h 06 min504 subs |
| Bortle 6Bright suburban | 12 min50 subs | 49 min198 subs | 3 h 17 min789 subs |
| Bortle 7Suburban / urban transition | 21 min84 subs | 1 h 23 min333 subs | 5 h 33 min1,331 subs |
| Bortle 8City | 34 min136 subs | 2 h 16 min544 subs | 9 h 03 min2,174 subs |
| Bortle 9Inner city | 1 h 02 min249 subs | 4 h 08 min993 subs | 17 h3,971 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 04 min of run time. The DWARF 3’s battery (rated about 5 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 20000mAh 18W18 W PD input and it runs while charging; needs a C-to-C cable for PD.
- 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 3 →
How it frames
The M9 is 12′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 12% of the frame’s short side.
Longer subs
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 20 min79 subs | 31 min126 subs | 1 h 23 min333 subs |
| 30 s | 19 min38 subs | 30 min61 subs | 1 h 22 min165 subs |
| 60 s | 30 min30 subs | 30 min30 subs | 1 h 22 min82 subs |
Leave the dual-band filter out for the M9. 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 10 times slower.
About the M9
A small globular near the galactic centre, slightly dimmed by dust. Compact and easy.
NGC 6333 · Globular cluster in Ophiuchus · magnitude 7.7 · 12′ · 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 3
Small pixels on a 35 mm f/4.3 lens give a sharper image than its aperture suggests, and EQ mode with 60 s subs makes it the read-noise winner in dark skies.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Three built-in filters: VIS, Astro (430 to 690 nm) and dual-band Hα 656 nm / OIII 501 nm.
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 60 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 M9 from a DWARF 3? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M9 with the ZWO Seestar S50: 34 min from Bortle 6
- M9 with the ZWO Seestar S50 Pro: 37 min from Bortle 6
- M9 with the ZWO Seestar S30: 35 min from Bortle 6
- M9 with the ZWO Seestar S30 Pro: 39 min from Bortle 6
- M9 with the DwarfLab DWARF mini: 34 min from Bortle 6
- M9 with the DwarfLab Draco: 28 min from Bortle 6
- M9 with the DwarfLab DWARF II: 1 h 54 min from Bortle 6
- M9 with the Vaonis Vespera II: 34 min from Bortle 6
- M9 with the Vaonis Vespera Pro: 1 h 15 min from Bortle 6
- M9 with the Vaonis Vespera 3: 32 min from Bortle 6
- M9 with the Vaonis Vespera Pro 2: 1 h 12 min from Bortle 6
- M9 with the Unistellar eQuinox 2: 30 min from Bortle 6
- M9 with the Unistellar Odyssey: 2 h 17 min from Bortle 6
- M9 with the Celestron Origin: 9 min from Bortle 6
- M9 with the Celestron Origin Mark II: 12 min from Bortle 6