M33 — Triangulum Galaxy

M33 sits roughly 2.7 million light-years from Earth — slightly farther than Andromeda — and forms, along with M31 and the Milky Way, the gravitational backbone of the Local Group. From dark skies it is a naked-eye object, but its low surface brightness makes it notoriously elusive: it is large but diffuse, easier to find with averted vision than through high magnification. The galaxy is rich in star-forming HII regions, the most prominent being NGC 604, a glowing pink complex ~1,500 light-years across — large enough that it appears as a distinct catalogued object in many surveys. For imagers, M33 rewards generous total integration. Long exposures with broadband filters bring out the loosely wound spiral arms, while pure Hα captures pull the HII regions out from the spiral background like a constellation of pink jewels. Recent radio observations suggest a tidal bridge of hydrogen connects M33 to M31 — they may have had a close encounter billions of years ago.

// imaging sessions

session // 02

11.10.2025 OSC broadband — 200P + 183CA (deeper re-shoot)

Gear: Sky-Watcher Explorer 200P Newtonian · Sky-Watcher EQ5 Pro SynScan GoTo · ToupTek 183CA · TS-Optics 2" Newtonian coma corrector · Pegasus Astro Gemini EAF · 50/90 mm guide / finder scope · ToupTek 327C Mini guide camera
Filters / frames: None — bare OSC broadband
Total integration: ~4 h
Sensor: gain 100
Location: Klebe, Plau am See, Mecklenburg · Bortle 3
Software: N.I.N.A. (Nighttime Imaging 'N' Astronomy) · Siril · GIMP · PHD2

Second visit to M33 from Plau am See — deeper integration than the September attempt, tighter framing on the galaxy core. The dust lanes and pink HII regions along the spiral arms (NGC 604 prominent in the upper-east) come through more clearly.

Messier 33 (Triangulum Galaxy) — face-on spiral, deeper Plau am See session 11 Oct 2025

M33 — Triangulum (Oct 2025 — final)

M33 — Triangulum (Oct 2025 — dust detail)

M33 — Triangulum (Oct 2025 — mid stretch)

M33 — Triangulum (Oct 2025 — wider)

session // 01

06.09.2025 OSC broadband — 200P + 183CA from Plau am See

Gear: Sky-Watcher Explorer 200P Newtonian · Sky-Watcher EQ5 Pro SynScan GoTo · ToupTek 183CA · TS-Optics 2" Newtonian coma corrector · Pegasus Astro Gemini EAF · 50/90 mm guide / finder scope · ToupTek 327C Mini guide camera
Filters / frames: None — bare OSC broadband
Total integration: ~4–5 h
Sensor: gain 100
Location: Klebe, Plau am See, Mecklenburg · Bortle 3
Software: N.I.N.A. (Nighttime Imaging 'N' Astronomy) · Siril · GIMP · PHD2

Triangulum Galaxy from the September 2025 Plau am See campaign — same week as the Bubble Nebula. OSC 183CA at f/5 with no filter; the dust lanes and blue OB associations along the spiral arms come through cleanly thanks to the Bortle 3 sky. PHD2 guiding via the 50/90 + 327C, autofocus per filter via the Pegasus EAF.

Messier 33 (Triangulum Galaxy) — face-on spiral in the Local Group, photographed from Plau am See on 6 Sep 2025

M33 — Triangulum Galaxy (final)

M33 — Triangulum Galaxy (variant 2)

M33 — Triangulum Galaxy (LRGB master)

M33 — Triangulum Galaxy (early processing)