How long to image the Abell 39 with the ZWO Seestar S30 Pro
From a Bortle 6 suburban sky, the ZWO Seestar S30 Pro needs about 26 h (9,526 subs of 10 s with the built-in dual-band (LP filter) filter) for a solid image of the Abell 39. A quick look takes 6 h 37 min; a showpiece 110+ h. Under a Bortle 3 rural sky the solid figure drops to 18 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 47 pixels across.
| Sky | Quick lookTarget obvious, still noisy | SolidClean enough to share | ShowpieceSmooth faint detail, print-worthy |
|---|---|---|---|
| Bortle 1Excellent dark site | 4 h 19 min1,555 subs | 17 h6,220 subs | 69 h24,879 subs |
| Bortle 2Typical dark site | 4 h 23 min1,581 subs | 18 h6,322 subs | 70 h25,285 subs |
| Bortle 3Rural | 4 h 31 min1,629 subs | 18 h6,514 subs | 72 h26,053 subs |
| Bortle 4Rural / suburban transition | 4 h 51 min1,745 subs | 19 h6,979 subs | 78 h27,914 subs |
| Bortle 5Suburban | 5 h 21 min1,929 subs | 21 h7,716 subs | 86 h30,864 subs |
| Bortle 6Bright suburban | 6 h 37 min2,382 subs | 26 h9,526 subs | 110+ h38,102 subs |
| Bortle 7Suburban / urban transition | 9 h 01 min3,244 subs | 36 h12,974 subs | 140+ h51,893 subs |
| Bortle 8City | 13 h4,582 subs | 51 h18,327 subs | 200+ h73,306 subs |
| Bortle 9Inner city | 21 h7,436 subs | 83 h29,744 subs | 330+ h118,973 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 53 min each. The Seestar S30 Pro’s battery is rated at about 5 h, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C power bank 10000mAh 5V 3A5 V 3 A input and it runs while charging.
- Seestar S30 Pro dew shieldActive anti-dew is built in; a shield adds margin. The S30 Pro front differs from the S30, so check the listing.
- 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 Seestar S30 Pro →
How it frames
The Abell 39 is 2.9′ across. The Seestar S30 Pro frames 3.99° × 2.24° at 3.74″ per pixel, so it is small in the frame, about 47 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
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 18 h6,514 subs | 21 h7,716 subs | 36 h12,974 subs |
| 20 s | 12 h2,189 subs | 15 h2,790 subs | 30 h5,419 subs |
| 30 s | 10 h1,222 subs | 14 h1,623 subs | 28 h3,375 subs |
| 60 s | 8 h 12 min492 subs | 12 h693 subs | 26 h1,569 subs |
With and without the dual-band filter
| Filter | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| UV/IR-cut (no light-pollution filter) | 15 h5,525 subs | 26 h9,454 subs | 74 h26,627 subs |
| dual-band (LP filter) | 18 h6,514 subs | 21 h7,716 subs | 36 h12,974 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 ZWO Seestar S30 Pro
The S30 optics upgraded to a quadruplet in front of an 8 MP IMX585. Same speed per pixel as the S30, four times the pixels, so you can crop hard.
10, 20 and 30 s in Alt-Az; 60 s only in EQ mode, which needs the TH10 head. Built-in UV/IR-cut, dual-band (OIII 30 nm / Hα 20 nm) and dark filters on the telephoto camera.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 10 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 Seestar S30 Pro? 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 DwarfLab DWARF 3: 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 Seestar S30 Pro