How long to image the Abell 39 with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 26 h (6,290 subs of 15 s with the built-in dual-band filter) for a solid image of the Abell 39. A quick look takes 6 h 33 min; a showpiece 100+ h. Under a Bortle 3 rural sky the solid figure drops to 15 h. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 3% 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 h 26 min825 subs | 14 h3,298 subs | 55 h13,192 subs |
| Bortle 2Typical dark site | 3 h 32 min848 subs | 14 h3,390 subs | 56 h13,560 subs |
| Bortle 3Rural | 3 h 43 min891 subs | 15 h3,564 subs | 59 h14,255 subs |
| Bortle 4Rural / suburban transition | 4 h 09 min997 subs | 17 h3,985 subs | 66 h15,940 subs |
| Bortle 5Suburban | 4 h 51 min1,164 subs | 19 h4,653 subs | 78 h18,610 subs |
| Bortle 6Bright suburban | 6 h 33 min1,573 subs | 26 h6,290 subs | 100+ h25,160 subs |
| Bortle 7Suburban / urban transition | 9 h 48 min2,353 subs | 39 h9,411 subs | 160+ h37,643 subs |
| Bortle 8City | 15 h3,564 subs | 59 h14,256 subs | 240+ h57,023 subs |
| Bortle 9Inner city | 26 h6,148 subs | 100+ h24,589 subs | 410+ h98,356 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 34 h of run time. That is more than one night: over 5 nights, about 6 h 49 min each. The DWARF 3’s battery is rated at about 5 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 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 Abell 39 is 2.9′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 3% 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 | 15 h3,564 subs | 19 h4,653 subs | 39 h9,411 subs |
| 30 s | 12 h1,467 subs | 17 h2,011 subs | 37 h4,391 subs |
| 60 s | 11 h655 subs | 15 h927 subs | 35 h2,117 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| Astro (no light-pollution filter) | 16 h3,858 subs | 31 h7,414 subs | 96 h22,958 subs |
| dual-band | 15 h3,564 subs | 19 h4,653 subs | 39 h9,411 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 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 Abell 39 from a DWARF 3? 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 mini: 21 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 3