How long to image the M74 with the DwarfLab DWARF 3
From a Bortle 6 suburban sky, the DwarfLab DWARF 3 needs about 7 h 59 min (1,916 subs of 15 s) for a solid image of the M74. A quick look takes 2 h; a showpiece 32 h. Under a Bortle 3 rural sky the solid figure drops to 2 h 36 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 10% 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 | 31 min125 subs | 2 h 04 min497 subs | 8 h 16 min1,985 subs |
| Bortle 2Typical dark site | 34 min135 subs | 2 h 15 min540 subs | 9 h2,159 subs |
| Bortle 3Rural | 39 min156 subs | 2 h 36 min623 subs | 10 h2,489 subs |
| Bortle 4Rural / suburban transition | 51 min206 subs | 3 h 26 min823 subs | 14 h3,289 subs |
| Bortle 5Suburban | 1 h 11 min285 subs | 4 h 45 min1,139 subs | 19 h4,555 subs |
| Bortle 6Bright suburban | 2 h479 subs | 7 h 59 min1,916 subs | 32 h7,664 subs |
| Bortle 7Suburban / urban transition | 3 h 32 min850 subs | 14 h3,397 subs | 57 h13,587 subs |
| Bortle 8City | 5 h 56 min1,424 subs | 24 h5,696 subs | 95 h22,783 subs |
| Bortle 9Inner city | 11 h2,650 subs | 44 h10,599 subs | 180+ h42,396 subs |
Power and kit for this session
Allowing for slewing, focusing and rejected subs, that is about 10 h of run time. That is more than one night: over 2 nights, about 5 h 11 min each. The DWARF 3’s battery is rated at about 5 h 30 min, which is cutting it fine; take a power bank. (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 M74 is 10′ × 9.5′ across. The DWARF 3 frames 2.93° × 1.65° at 2.75″ per pixel, so it fills 10% 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 | 2 h 36 min623 subs | 4 h 45 min1,139 subs | 14 h3,397 subs |
| 30 s | 2 h 24 min289 subs | 4 h 33 min547 subs | 14 h1,676 subs |
| 60 s | 2 h 19 min139 subs | 4 h 28 min268 subs | 14 h833 subs |
Leave the dual-band filter out for the M74. 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 M74
A perfect face-on spiral with very low surface brightness, hence the nickname. One of the hardest Messier objects for small scopes.
NGC 628, Phantom Galaxy · Galaxy in Pisces · magnitude 9.4 · 10′ × 9.5′ · best in Sep, Oct, Nov. 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 M74 from a DWARF 3? Email it with your total time and sky to [email protected] and it goes here, credited.
Same target, other telescopes
- M74 with the ZWO Seestar S50: 5 h 30 min from Bortle 6
- M74 with the ZWO Seestar S50 Pro: 6 h 02 min from Bortle 6
- M74 with the ZWO Seestar S30: 5 h 48 min from Bortle 6
- M74 with the ZWO Seestar S30 Pro: 6 h 23 min from Bortle 6
- M74 with the DwarfLab DWARF mini: 5 h 29 min from Bortle 6
- M74 with the DwarfLab Draco: 4 h 31 min from Bortle 6
- M74 with the DwarfLab DWARF II: 19 h from Bortle 6
- M74 with the Vaonis Vespera II: 5 h 30 min from Bortle 6
- M74 with the Vaonis Vespera Pro: 12 h from Bortle 6
- M74 with the Vaonis Vespera 3: 5 h 16 min from Bortle 6
- M74 with the Vaonis Vespera Pro 2: 12 h from Bortle 6
- M74 with the Unistellar eQuinox 2: 5 h 03 min from Bortle 6
- M74 with the Unistellar Odyssey: 23 h from Bortle 6
- M74 with the Celestron Origin: 1 h 27 min from Bortle 6
- M74 with the Celestron Origin Mark II: 1 h 59 min from Bortle 6