How long to image the Abell 39 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 160+ h (143,070 subs of 4 s) for a solid image of the Abell 39. A quick look takes 40 h; a showpiece 640+ h. Under a Bortle 3 rural sky the solid figure drops to 100+ h. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 9% 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 | 25 h22,316 subs | 99 h89,262 subs | 400+ h357,045 subs |
| Bortle 2Typical dark site | 25 h22,729 subs | 100+ h90,914 subs | 400+ h363,655 subs |
| Bortle 3Rural | 26 h23,510 subs | 100+ h94,040 subs | 420+ h376,160 subs |
| Bortle 4Rural / suburban transition | 28 h25,404 subs | 110+ h101,614 subs | 450+ h406,456 subs |
| Bortle 5Suburban | 32 h28,405 subs | 130+ h113,618 subs | 500+ h454,471 subs |
| Bortle 6Bright suburban | 40 h35,768 subs | 160+ h143,070 subs | 640+ h572,277 subs |
| Bortle 7Suburban / urban transition | 55 h49,798 subs | 220+ h199,189 subs | 890+ h796,753 subs |
| Bortle 8City | 80 h71,581 subs | 320+ h286,321 subs | 1270+ h1,145,283 subs |
| Bortle 9Inner city | 130+ h118,037 subs | 520+ h472,148 subs | 2100+ h1,888,592 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 210+ h of run time. That is more than one night: over 30 nights, about 6 h 53 min each. The Odyssey’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 power bank 20000mAh 5V 2.4AUnistellar says plain 5 V 2.4 A and warns against fast or adaptive chargers.
- 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 Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 9% of the frame’s short side.
Filters
The Abell 39 is an emission target, where a dual-band filter would normally cut the time several-fold from a lit sky, but the Odyssey has no dual-band option: No filter option; Unistellar says third-party filters cannot be fitted to the Odyssey. The figures above are for the No filter position, and a darker sky is the lever that remains.
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 Unistellar Odyssey
Unistellar’s compact 85 mm with autofocus and tiny pixels. Sharp, but the fine sampling costs time on faint extended targets. The Odyssey Pro is the same telescope with an eyepiece added, so these figures apply to both.
Fixed 4 s subs in Enhanced Vision; they cannot be changed. No filter option; Unistellar says third-party filters cannot be fitted to the Odyssey.
The Odyssey uses fixed 4 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 Abell 39 from a Odyssey? 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 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 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 Odyssey