M106 — Spiral Galaxy

Sat, 02 May 2026 21:00:00 +0200

Messier 106 (NGC 4258) is a bright, nearby spiral galaxy in Canes Venatici, about 23 million light‑years away. Classified roughly as SAB(s)bc, it shows a luminous central bulge and broad, patchy arms laced with dust and H II regions. Deep images reveal a faint outer disc and subtle tidal extensions; in total the galaxy stretches roughly 18 × 7 arcminutes on the sky — some 80,000 light‑years across at its distance.

Discovered by Pierre Méchain in 1781 and added to the Messier catalogue shortly thereafter, M106 has become a touchstone object in modern astronomy thanks to its water‑vapour megamasers. Radio interferometry maps a thin disc of masing clouds orbiting the central black hole, allowing a geometric distance measurement. That precise distance helped anchor the extragalactic distance ladder and refine estimates of the Hubble constant.

From mid‑northern latitudes M106 is a spring target, riding high from March to May not far from the handle of the Big Dipper. In small telescopes it appears as an elongated haze with a bright, condensed core; medium apertures begin to show a dust lane and mottling in the inner arms. Under suburban Bortle 5 skies, long integrations are key to teasing out the dim halo and lopsided outer structure.

M106 sits in a small group: the diminutive companion NGC 4248 lies just to the north‑east, while several faint dwarf galaxies and background systems pepper the field. The galaxy’s famous “anomalous” arms — powered by activity in the nucleus — cut across the normal spiral pattern; in broadband images they often register as asymmetric glow and filamentary plumes rather than sharp dust lanes.

This image was captured with a 150/750 mm Newtonian and a colour CMOS camera. An Optolong L-Pro 2" light‑pollution filter helped tame gradients under Bortle 5 conditions; 64 × 180‑second sub‑exposures (3h 12min total) were calibrated and combined, then carefully processed to balance the bright core against the very faint outskirts.

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Telescope	SkyWatcher 150/750P
Mount	ZWO AM3N
Camera	ZWO ASI2600MC Pro
Filters	Optolong L-Pro 2"
Exposure	64 × 180s (3h 12min)
Bortle	5
Moon	Waning gibbous (99.5%)
Processing	SetiAstro Suite Pro, Prism Deep, Axiom V2, Graxpert, CosmicClarity, Siril

NGC 4258 on AstroT3k

M106 — Spiral Galaxy

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