How long to image the Abell 39 with the DwarfLab DWARF mini
From a Bortle 6 suburban sky, the DwarfLab DWARF mini needs about 21 h (5,130 subs of 15 s with the built-in dual-band filter) for a solid image of the Abell 39. A quick look takes 5 h 21 min; a showpiece 85 h. Under a Bortle 3 rural sky the solid figure drops to 14 h. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it is small in the frame, about 44 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 3 h 20 min799 subs | 13 h3,193 subs | 53 h12,770 subs |
| Bortle 2Typical dark site | 3 h 23 min813 subs | 14 h3,252 subs | 54 h13,008 subs |
| Bortle 3Rural | 3 h 30 min842 subs | 14 h3,365 subs | 56 h13,458 subs |
| Bortle 4Rural / suburban transition | 3 h 47 min910 subs | 15 h3,637 subs | 61 h14,548 subs |
| Bortle 5Suburban | 4 h 14 min1,018 subs | 17 h4,070 subs | 68 h16,277 subs |
| Bortle 6Bright suburban | 5 h 21 min1,283 subs | 21 h5,130 subs | 85 h20,518 subs |
| Bortle 7Suburban / urban transition | 7 h 27 min1,788 subs | 30 h7,150 subs | 120+ h28,598 subs |
| Bortle 8City | 11 h2,572 subs | 43 h10,287 subs | 170+ h41,145 subs |
| Bortle 9Inner city | 18 h4,244 subs | 71 h16,976 subs | 280+ h67,903 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 28 h of run time. That is more than one night: over 4 nights, about 6 h 57 min each. The DWARF mini’s battery is rated at about 3 h 30 min, so each night needs an external power bank. (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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How it frames
The Abell 39 is 2.9′ across. The DWARF mini frames 2.13° × 1.20° at 3.99″ per pixel, so it is small in the frame, about 44 pixels across. It is worth doing, but the result is a crop rather than a full frame; a longer focal length would resolve more of it.
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 | 14 h3,365 subs | 17 h4,070 subs | 30 h7,150 subs |
| 30 s | 9 h 37 min1,154 subs | 13 h1,507 subs | 25 h3,047 subs |
| 60 s | 7 h 25 min445 subs | 10 h622 subs | 23 h1,392 subs |
| 90 s | 6 h 41 min268 subs | 9 h 37 min385 subs | 22 h899 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 13 h3,016 subs | 22 h5,318 subs | 64 h15,381 subs |
| dual-band | 14 h3,365 subs | 17 h4,070 subs | 30 h7,150 subs |
About the Abell 39
A near-perfect faint sphere in Hercules. Very low surface brightness, an OIII target for dark skies and long dual-band stacks.
PN A66 39 · Planetary nebula in Hercules · magnitude 13.7 · 2.9′ · best in May, Jun, Jul. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Planetary nebulae are small but intensely bright per pixel in OIII and H-alpha, so they respond very well to a dual-band filter and do not need much time for the main shell. The faint outer halos most of them have are a different proposition and need hours. Keep subs short if the central region saturates.
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 Abell 39 from a DWARF mini? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- Abell 39 with the ZWO Seestar S50: 22 h from Bortle 6
- Abell 39 with the ZWO Seestar S50 Pro: 24 h from Bortle 6
- Abell 39 with the ZWO Seestar S30: 26 h from Bortle 6
- Abell 39 with the ZWO Seestar S30 Pro: 26 h from Bortle 6
- Abell 39 with the DwarfLab DWARF 3: 26 h from Bortle 6
- Abell 39 with the DwarfLab Draco: 17 h from Bortle 6
- Abell 39 with the DwarfLab DWARF II: 130+ h from Bortle 6
- Abell 39 with the Vaonis Vespera II: 37 h from Bortle 6
- Abell 39 with the Vaonis Vespera Pro: 83 h from Bortle 6
- Abell 39 with the Vaonis Vespera 3: 35 h from Bortle 6
- Abell 39 with the Vaonis Vespera Pro 2: 79 h from Bortle 6
- Abell 39 with the Unistellar eQuinox 2: 34 h from Bortle 6
- Abell 39 with the Unistellar Odyssey: 160+ h from Bortle 6
- Abell 39 with the Celestron Origin: 9 h 41 min from Bortle 6
- Abell 39 with the Celestron Origin Mark II: 13 h from Bortle 6
All telescopes for the Abell 39 · All targets for the DWARF mini