How long to image the NGC 2903 with the Vaonis Vespera 3
From a Bortle 6 suburban sky, the Vaonis Vespera 3 needs about 2 h 15 min (809 subs of 10 s) for a solid image of the NGC 2903. A quick look takes 34 min; a showpiece 8 h 59 min. Under a Bortle 3 rural sky the solid figure drops to 51 min. At Bortle 6 the limit is skyglow, so a darker site or a filter helps more than longer subs. In this scope's field it fills 14% 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 | 11 min64 subs | 43 min256 subs | 2 h 50 min1,021 subs |
| Bortle 2Typical dark site | 11 min69 subs | 45 min273 subs | 3 h 01 min1,089 subs |
| Bortle 3Rural | 13 min77 subs | 51 min305 subs | 3 h 23 min1,218 subs |
| Bortle 4Rural / suburban transition | 16 min96 subs | 1 h 04 min383 subs | 4 h 15 min1,529 subs |
| Bortle 5Suburban | 21 min127 subs | 1 h 24 min506 subs | 5 h 37 min2,023 subs |
| Bortle 6Bright suburban | 34 min203 subs | 2 h 15 min809 subs | 8 h 59 min3,235 subs |
| Bortle 7Suburban / urban transition | 58 min347 subs | 3 h 51 min1,386 subs | 15 h5,544 subs |
| Bortle 8City | 1 h 35 min571 subs | 6 h 20 min2,283 subs | 25 h9,130 subs |
| Bortle 9Inner city | 2 h 55 min1,049 subs | 12 h4,194 subs | 47 h16,776 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 2 h 55 min of run time. The Vespera 3’s battery (rated about 11 h) should cover it; a power bank still keeps the phone running the app alive. (Bortle 6, solid image; we allow 30% over the integration time, and 30% off the battery for a February night.)
- USB-C PD power bank 20000mAh 30WVaonis says an external bank extends sessions; 30 W PD as for the II and Pro.
- 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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How it frames
The NGC 2903 is 12.6′ × 6′ across. The Vespera 3 frames 2.60° × 1.46° at 2.44″ per pixel, so it fills 14% of the frame’s short side.
Longer subs
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic widens the field to 4.3° × 2.4°. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 51 min305 subs | 1 h 24 min506 subs | 3 h 51 min1,386 subs |
| 20 s | 43 min130 subs | 1 h 17 min231 subs | 3 h 43 min671 subs |
| 30 s | 41 min82 subs | 1 h 14 min149 subs | 3 h 41 min442 subs |
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 Vaonis Vespera 3
The 2026 Vespera: same 50 mm quadruplet class as the II on an 8 MP IMX585, with a 24 MP mosaic mode and 11 hours of battery. Per pixel it behaves like a Seestar S50 Pro without the built-in dual-band filter.
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic widens the field to 4.3° × 2.4°. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar. The new optical baffle is not a substitute for a CLS filter.
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 30 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 NGC 2903 from a Vespera 3? 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 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 Unistellar Odyssey: 9 h 55 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 Vespera 3