How long to image the M105 with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 1 h 27 min (348 subs of 15 s) for a solid image of the M105. A quick look takes 22 min; a showpiece 5 h 48 min. Under a Bortle 3 rural sky the solid figure drops to 35 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 5% 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 | 7 min30 subs | 30 min119 subs | 1 h 58 min474 subs |
| Bortle 2Typical dark site | 8 min32 subs | 31 min126 subs | 2 h 05 min502 subs |
| Bortle 3Rural | 9 min35 subs | 35 min139 subs | 2 h 19 min556 subs |
| Bortle 4Rural / suburban transition | 11 min43 subs | 43 min172 subs | 2 h 51 min685 subs |
| Bortle 5Suburban | 14 min56 subs | 56 min223 subs | 3 h 42 min889 subs |
| Bortle 6Bright suburban | 22 min87 subs | 1 h 27 min348 subs | 5 h 48 min1,391 subs |
| Bortle 7Suburban / urban transition | 37 min147 subs | 2 h 27 min587 subs | 9 h 47 min2,347 subs |
| Bortle 8City | 1 h240 subs | 3 h 59 min958 subs | 16 h3,831 subs |
| Bortle 9Inner city | 1 h 49 min438 subs | 7 h 17 min1,750 subs | 29 h6,997 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 1 h 53 min of run time. The DWARF 3’s battery (rated about 5 h 30 min) 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.)
- USB-C PD power bank 20000mAh 18W18 W PD input and it runs while charging; needs a C-to-C cable for PD.
- 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 DWARF 3 →
How it frames
The M105 is 5.4′ × 4.8′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 5% of the frame’s short side.
Longer subs
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Time for a solid image by sub length:
| Sub length | Bortle 3 | Bortle 5 | Bortle 7 |
|---|---|---|---|
| 15 s | 35 min139 subs | 56 min223 subs | 2 h 27 min587 subs |
| 30 s | 33 min66 subs | 54 min108 subs | 2 h 25 min290 subs |
| 60 s | 32 min32 subs | 53 min53 subs | 2 h 24 min144 subs |
Leave the dual-band filter out for the M105. It is a galaxy, and it shines right across the spectrum. A dual-band filter keeps two emission lines and throws the rest away, so most of the light you came for is being stopped along with the sky. From a Bortle 6 sky it would be roughly 10 times slower.
About the M105
An elliptical in the Leo I group, with NGC 3384 and NGC 3389 forming a tight trio.
NGC 3379 · Galaxy in Leo · magnitude 9.3 · 5.4′ × 4.8′ · 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 DwarfLab DWARF 3
Small pixels on a 35 mm f/4.3 lens give a sharper image than its aperture suggests, and EQ mode with 60 s subs makes it the read-noise winner in dark skies.
Auto mode caps subs at 15 s; 30 s and longer need EQ mode, and 60 s is the ceiling on the tele camera. Three built-in filters: VIS, Astro (430 to 690 nm) and dual-band Hα 656 nm / OIII 501 nm.
Longer subs matter most under dark skies, where read noise rather than skyglow sets the floor. From a city the difference between 15 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 M105 from a DWARF 3? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M105 with the ZWO Seestar S50: 1 h from Bortle 6
- M105 with the ZWO Seestar S50 Pro: 1 h 05 min from Bortle 6
- M105 with the ZWO Seestar S30: 1 h 02 min from Bortle 6
- M105 with the ZWO Seestar S30 Pro: 1 h 09 min from Bortle 6
- M105 with the DwarfLab DWARF mini: 59 min from Bortle 6
- M105 with the DwarfLab Draco: 49 min from Bortle 6
- M105 with the DwarfLab DWARF II: 3 h 21 min from Bortle 6
- M105 with the Vaonis Vespera II: 1 h from Bortle 6
- M105 with the Vaonis Vespera Pro: 2 h 13 min from Bortle 6
- M105 with the Vaonis Vespera 3: 57 min from Bortle 6
- M105 with the Vaonis Vespera Pro 2: 2 h 07 min from Bortle 6
- M105 with the Unistellar eQuinox 2: 53 min from Bortle 6
- M105 with the Unistellar Odyssey: 4 h 01 min from Bortle 6
- M105 with the Celestron Origin: 16 min from Bortle 6
- M105 with the Celestron Origin Mark II: 22 min from Bortle 6