How long to image the NGC 2903 with the Unistellar Odyssey
From a Bortle 6 suburban sky, the Unistellar Odyssey needs about 9 h 55 min (8,932 subs of 4 s) for a solid image of the NGC 2903. A quick look takes 2 h 29 min; a showpiece 40 h. Under a Bortle 3 rural sky the solid figure drops to 6 h 37 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 37% 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 | 1 h 34 min1,416 subs | 6 h 18 min5,664 subs | 25 h22,655 subs |
| Bortle 2Typical dark site | 1 h 36 min1,441 subs | 6 h 24 min5,764 subs | 26 h23,056 subs |
| Bortle 3Rural | 1 h 39 min1,489 subs | 6 h 37 min5,954 subs | 26 h23,816 subs |
| Bortle 4Rural / suburban transition | 1 h 47 min1,604 subs | 7 h 08 min6,414 subs | 29 h25,655 subs |
| Bortle 5Suburban | 1 h 59 min1,786 subs | 7 h 56 min7,143 subs | 32 h28,571 subs |
| Bortle 6Bright suburban | 2 h 29 min2,233 subs | 9 h 55 min8,932 subs | 40 h35,725 subs |
| Bortle 7Suburban / urban transition | 3 h 26 min3,085 subs | 14 h12,339 subs | 55 h49,356 subs |
| Bortle 8City | 4 h 54 min4,408 subs | 20 h17,631 subs | 78 h70,521 subs |
| Bortle 9Inner city | 8 h 02 min7,229 subs | 32 h28,915 subs | 130+ h115,658 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 13 h of run time. That is more than one night: over 2 nights, about 6 h 27 min each. The Odyssey’s battery is rated at about 5 h, less near freezing, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a February night.)
- 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.
- hand warmers long lastingAir-activated packs give hours of heat for the person; winter nights are long and you spend most of them standing still.
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Everything that fits the Odyssey →
How it frames
The NGC 2903 is 12.6′ × 6′ across. The Odyssey frames 0.75° × 0.56° at 0.93″ per pixel, so it fills 37% of the frame’s short side.
About the NGC 2903
A bright barred spiral below the Sickle of Leo that Messier somehow missed. Bright core, well-defined arms.
UGC 5079 · Galaxy in Leo · magnitude 9.0 · 12.6′ × 6′ · best in Jan, Feb, Mar. Reachable from mid-northern latitudes (UK, northern US, central Europe) and from the south.
Galaxies are broadband targets: their light is mostly starlight spread across the spectrum, so a dual-band filter throws most of it away and makes things slower, not faster. Shoot without a filter (or with a plain UV/IR cut) and rely on total time and a dark sky. The core of a galaxy is usually many times brighter than its outer disc, so a short stack shows the nucleus long before the arms; the figures here are for the arms and disc, not the core.
Field rotation in Alt-Az mode crops the edges of the stack over a long session, so on a big galaxy re-centre now and then or use EQ mode where your scope supports it.
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 NGC 2903 from a Odyssey? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- NGC 2903 with the ZWO Seestar S50: 2 h 21 min from Bortle 6
- NGC 2903 with the ZWO Seestar S50 Pro: 2 h 34 min from Bortle 6
- NGC 2903 with the ZWO Seestar S30: 2 h 28 min from Bortle 6
- NGC 2903 with the ZWO Seestar S30 Pro: 2 h 44 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF 3: 3 h 25 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF mini: 2 h 20 min from Bortle 6
- NGC 2903 with the DwarfLab Draco: 1 h 56 min from Bortle 6
- NGC 2903 with the DwarfLab DWARF II: 8 h 04 min from Bortle 6
- NGC 2903 with the Vaonis Vespera II: 2 h 21 min from Bortle 6
- NGC 2903 with the Vaonis Vespera Pro: 5 h 16 min from Bortle 6
- NGC 2903 with the Vaonis Vespera 3: 2 h 15 min from Bortle 6
- NGC 2903 with the Vaonis Vespera Pro 2: 5 h 01 min from Bortle 6
- NGC 2903 with the Unistellar eQuinox 2: 2 h 08 min from Bortle 6
- NGC 2903 with the Celestron Origin: 37 min from Bortle 6
- NGC 2903 with the Celestron Origin Mark II: 51 min from Bortle 6
All telescopes for the NGC 2903 · All targets for the Odyssey