How long to image the M109 with the Vaonis Vespera Pro 2
From a Bortle 6 suburban sky, the Vaonis Vespera Pro 2 needs about 8 h 07 min (2,924 subs of 10 s) for a solid image of the M109. A quick look takes 2 h 02 min; a showpiece 32 h. Under a Bortle 3 rural sky the solid figure drops to 3 h 22 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 8% 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 | 43 min261 subs | 2 h 54 min1,044 subs | 12 h4,175 subs |
| Bortle 2Typical dark site | 46 min276 subs | 3 h 04 min1,102 subs | 12 h4,406 subs |
| Bortle 3Rural | 50 min303 subs | 3 h 22 min1,211 subs | 13 h4,843 subs |
| Bortle 4Rural / suburban transition | 1 h 01 min369 subs | 4 h 06 min1,476 subs | 16 h5,901 subs |
| Bortle 5Suburban | 1 h 19 min474 subs | 5 h 16 min1,895 subs | 21 h7,579 subs |
| Bortle 6Bright suburban | 2 h 02 min731 subs | 8 h 07 min2,924 subs | 32 h11,696 subs |
| Bortle 7Suburban / urban transition | 3 h 24 min1,222 subs | 14 h4,885 subs | 54 h19,540 subs |
| Bortle 8City | 5 h 30 min1,983 subs | 22 h7,930 subs | 88 h31,719 subs |
| Bortle 9Inner city | 10 h3,606 subs | 40 h14,424 subs | 160+ h57,693 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 11 h of run time. That is more than one night: over 2 nights, about 5 h 17 min each. The Vespera Pro 2’s battery (rated about 11 h) should cover each night; a power bank still keeps the phone running the app alive. (Bortle 6, solid image; we allow 30% over the integration time.)
- USB-C PD power bank 20000mAh 30WExternal bank extends the 11 h battery.
- 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 M109 is 7.6′ × 4.7′ across. The Vespera Pro 2 frames 1.65° × 1.65° at 1.68″ per pixel, so it fills 8% 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 gives 3.2° × 3.2° at 50 MP. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 10 s | 3 h 22 min1,211 subs | 5 h 16 min1,895 subs | 14 h4,885 subs |
| 20 s | 2 h 47 min502 subs | 4 h 41 min844 subs | 13 h2,339 subs |
| 30 s | 2 h 36 min312 subs | 4 h 30 min540 subs | 13 h1,537 subs |
About the M109
A barred spiral next to Phecda in the Plough. Faint outer arms, bright bar.
NGC 3992 · Galaxy in Ursa Major · magnitude 9.8 · 7.6′ × 4.7′ · best in Feb, Mar, Apr. 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 Pro 2
The square-sensor 2026 Vespera with 2 µm pixels. Sharper than the Vespera 3 on small targets and correspondingly slower per pixel; the 12.5 MP square frame suits galaxies and planetaries.
10 s subs by default; Expert Mode manual targets allow 1 to 30 s. Alt-azimuth only; CovalENS mosaic gives 3.2° × 3.2° at 50 MP. Optional clip-on Vaonis filters: dual-band, light-pollution (CLS) and solar.
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 M109 from a Vespera Pro 2? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M109 with the ZWO Seestar S50: 3 h 48 min from Bortle 6
- M109 with the ZWO Seestar S50 Pro: 4 h 10 min from Bortle 6
- M109 with the ZWO Seestar S30: 4 h from Bortle 6
- M109 with the ZWO Seestar S30 Pro: 4 h 25 min from Bortle 6
- M109 with the DwarfLab DWARF 3: 5 h 31 min from Bortle 6
- M109 with the DwarfLab DWARF mini: 3 h 47 min from Bortle 6
- M109 with the DwarfLab Draco: 3 h 07 min from Bortle 6
- M109 with the DwarfLab DWARF II: 13 h from Bortle 6
- M109 with the Vaonis Vespera II: 3 h 48 min from Bortle 6
- M109 with the Vaonis Vespera Pro: 8 h 31 min from Bortle 6
- M109 with the Vaonis Vespera 3: 3 h 38 min from Bortle 6
- M109 with the Unistellar eQuinox 2: 3 h 28 min from Bortle 6
- M109 with the Unistellar Odyssey: 16 h from Bortle 6
- M109 with the Celestron Origin: 1 h from Bortle 6
- M109 with the Celestron Origin Mark II: 1 h 23 min from Bortle 6
All telescopes for the M109 · All targets for the Vespera Pro 2