Reflection Nebula on AstroT3k

NGC 7023 — Iris Nebula

Tue, 07 Apr 2026 21:00:00 +0200

NGC 7023, better known as the Iris Nebula, is a bright reflection nebula embedded in a vast complex of interstellar dust in the constellation Cepheus, roughly 1,300 light‑years away. Its characteristic blue hue comes from starlight scattered by fine dust grains surrounding the illuminating star HD 200775, a young Herbig Be star. The bright central bloom spans a good fraction of a degree when including the surrounding dusty filaments, while the most prominent core measures only several arcminutes across, framed by sweeping, dark lanes.

The nebula was discovered by William Herschel in 1794 and is catalogued as Caldwell 4 in modern observing lists. From mid‑northern latitudes it is circumpolar, riding high in the northern sky and best placed during late summer and autumn nights, though it can be followed throughout the year. In binoculars under dark skies, the field is rich with faint dust; small telescopes reveal the bright core and the soft, fan‑shaped glow.

The Iris sits within an extended web of dust often referred to as galactic cirrus (IFN). Long exposures bring out intricate, filamentary structures and sharp, dark lanes silhouetted against the diffuse glow. The scene rewards deep broadband imaging and careful processing to balance the delicate reflection signal with surrounding faint dust.


Telescope	SkyWatcher 150/750P
Mount	ZWO AM3N
Camera	ZWO ASI2600MC Pro
Filters	Optolong L-Pro 2"
Exposure	50 × 180s (2h 30min)
Bortle	5
Moon	Waning crescent (1.2%)
Processing	SetiAstro Suite Pro, Prism Deep, Axiom V2, Graxpert, CosmicClarity, Siril

M45 — Pleiades

Thu, 30 Oct 2025 21:00:00 +0100

The Pleiades (M45, Melotte 22) is one of the nearest and most recognisable open clusters in the sky, set in the constellation Taurus. It lies about 440 light‑years from Earth and is around 100 million years old. The cluster spans roughly two degrees on the sky — four times the apparent diameter of the Moon — and is dominated by hot, blue B‑type stars. Long exposures reveal extensive blue reflection nebulosity: interstellar dust grains scattering starlight. This dust is thought to be unrelated to the cluster’s birth cloud; instead, the Pleiades are currently passing through a filament of the Taurus molecular complex.

Visible to the naked eye even from suburban locations, the Pleiades are a rewarding target for binoculars and short‑focal‑length telescopes. Dozens of members are resolved in 10×50 binoculars, while wide‑field imaging captures the tangle of faint dust around the brightest stars. The best season in the northern hemisphere runs from late autumn through winter, when Taurus climbs high in the evening sky.

In deep images two named reflection nebulae stand out: NGC 1435 (the Merope Nebula) with its tapered “fan” of dust, and NGC 1432 around Maia. The cluster’s brightest star, Alcyone, anchors the central asterism commonly nicknamed the “Seven Sisters”, a motif present in many cultures since antiquity.


Telescope	SkyWatcher 150/750P
Mount	motorised EQ3-2
Camera	Canon 600D (astro-mod)
Exposure	145 × 173s (6h 58min)
Bortle	5
Moon	Waxing gibbous (58.0%)
Processing	Siril, GraXpert, CosmicClarity, Gimp