Triangulum Galaxy

“An Autumn Evening with the Pinwheel of Triangulum”

On 24 October 2024 a brilliant, 92 % gibbous Moon arched over the northern treetops. Most of the night-sky crowd headed indoors—moon-wash is the sworn enemy of faint galaxies, after all. Yet the CGEM mount whirred into life at 20:30, slewing the 80 mm refractor toward a patch of sky so dim it looked empty. The target sat three million light-years away:

Messier 33, the Triangulum Galaxy—compact, blue-tinged, restless with newborn suns.

I. A Spiral without a Heart

Unlike the Milky Way or Andromeda, M 33 sports no central bulge. Its disc is a playground of loosely wound arms humming with star-forming regions, the most famous of which—NGC 604—is large enough to swallow dozens of Orion Nebulae. Astronomers suspect Triangulum may be gravitationally flirting with Andromeda (and, by extension, us), a slow dance that could someday knit the Local Group’s three big spirals into one.

Angular size: 71 × 42 arc-minutes—stretching wider on the sky than the full Moon.

True span: ~60 000 light-years.

Brightness: Mag 5.7 (bright on paper, but surface-brightness low enough to drown in moonlight).

II. Harvesting Photons under a Moon-Bright Sky

L 90 60 1.5

R 30 60 0.5

G 30 60 0.5

B 30 60 0.5

H-α 20 300 1.7

Total integration ≈ 4.7 h

Guiding: 0.72″ RMS—steady as a metronome in 5 km h⁻¹ breezes.

Camera: ASI294MM Pro at –10 °C.

Filters: Antlia LRGB-V plus 3 nm H-α for the scarlet star-nurseries.

A perfect meridian flip at midnight and frequent autofocus tweaks kept stars needle-sharp despite an 8 °C chill.

III. Digital Alchemy

Calibrate & stack in PixInsight (20 flats, darks, flat-darks per channel).

Process LRGB first—dust off the workflow, stretch the faint outer arms until they glow silver-blue.

Blend H-α using an “L-enhance” trick: sprinkle the 3 nm data into the red channel, then pop the giant nebulae without overwhelming the galaxy’s pastel tones.

Local contrast (using HDRMT) teased out mottled dust lanes; star-size masks kept halos in check.

Final polish: gentle star reduction and a tiny dash of SCNR to tame Moon-induced gradients.

After two attempts the galaxy floated on-screen: spiral arms afire with pink H-II knots, a bluish starlight whirlpool with no bright core—Triangulum wearing its eternal youth like a badge.

IV. What the Session Taught

Moonlight isn’t fatal—short, rapid LRGB subs plus a deep H-α layer can out-smart a 93 % Moon.

Compact gear, big pay-off—an 80 mm scope and 60-second exposures drew out a galaxy 3 million light-years away.

Dynamic galaxies matter—M 33’s bulge-less disc hints we’re watching a spiral still growing, still assembling its identity.

By 03:00 the script parked the scope, and dew sparkled on the equipment.

On the monitor, Triangulum spun in delicate blues and rose-petal reds—a cosmic pinwheel frozen in time, bearing postcards from stellar nurseries that ignited when humanity’s ancestors were still fashioning stone tools.