How long to image the Pinwheel Galaxy with the DwarfLab DWARF II

From a Bortle 6 suburban sky, the DwarfLab DWARF II needs about 16 h (3,817 subs of 15 s) for a solid image of the Pinwheel Galaxy. A quick look takes 3 h 59 min; a showpiece 64 h. Under a Bortle 3 rural sky the solid figure drops to 7 h 44 min. At Bortle 6 the limit is a mix of skyglow and read noise. In this scope's field it fills 27% of the frame’s short side.

Pinwheel Galaxy with the DwarfLab DWARF II: 15 s subs.
SkyQuick lookTarget obvious, still noisySolidClean enough to shareShowpieceSmooth faint detail, print-worthy
Bortle 1Excellent dark site1 h 44 min417 subs6 h 56 min1,665 subs28 h6,660 subs
Bortle 2Typical dark site1 h 48 min433 subs7 h 13 min1,731 subs29 h6,924 subs
Bortle 3Rural1 h 56 min464 subs7 h 44 min1,856 subs31 h7,424 subs
Bortle 4Rural / suburban transition2 h 15 min540 subs9 h2,159 subs36 h8,635 subs
Bortle 5Suburban2 h 45 min660 subs11 h2,639 subs44 h10,555 subs
Bortle 6Bright suburban3 h 59 min955 subs16 h3,817 subs64 h15,266 subs
Bortle 7Suburban / urban transition6 h 19 min1,516 subs25 h6,061 subs100+ h24,242 subs
Bortle 8City9 h 57 min2,387 subs40 h9,545 subs160+ h38,178 subs
Bortle 9Inner city18 h4,244 subs71 h16,975 subs280+ h67,899 subs

Adjust in the calculator

Power and kit for this session

Allowing for slewing, focusing and rejected subs, that is about 21 h of run time. That is more than one night: over 3 nights, about 6 h 53 min each. The DWARF II’s battery is rated at about 3 h, so each night needs an external power bank. (Bortle 6, solid image; we allow 30% over the integration time.)

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How it frames

The Pinwheel Galaxy is 29′ × 27′ across. The DWARF II frames 3.19° × 1.79° at 2.99″ per pixel, so it fills 27% of the frame’s short side.

About the Pinwheel Galaxy

Big, face-on and faint. Its total magnitude is flattering; spread over half a degree the arms are dim and demand hours, especially from suburban skies.

M101, NGC 5457 · Galaxy in Ursa Major · magnitude 7.9 · 29′ × 27′ · best in Apr, May, Jun. 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 II

The original pocket scope. 24 mm aperture and tiny 1.45 µm pixels mean it is slow per pixel, so bin or downsample and be patient.

15 s is the hard maximum in any mode; DwarfLab recommends EQ mode at 15 s. Two built-in filters, VIS and Astro (IR-pass); no dual-band. The optional UHC filter is no longer sold.

The DWARF II uses fixed 15 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.

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Imaged the Pinwheel Galaxy with your DWARF II? Did the solid figure match?Anonymous, one tap. It is how the model gets calibrated.

Have an image of the Pinwheel Galaxy from a DWARF II? Email it with your total time and sky to [email protected] and it goes here, credited.

Same target, other telescopes

All telescopes for the Pinwheel Galaxy · All targets for the DWARF II