When is the best time to observe Iota Ceti?

Iota Ceti is best observed from August through October, with peak visibility during September when it transits around midnight in the Northern Hemisphere.

Where is Iota Ceti located in the sky?

Iota Ceti lies in the constellation Cetus at right ascension 00h 19m and declination -08° 49′.

What telescope do I need to split Iota Ceti?

Splitting Iota Ceti requires an aperture of roughly 60 mm or larger — the components are separated by about 106.4″ at magnitudes near 3.6. The companion is about 6.8 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Iota Ceti — Double Star in Cetus

DoubleStar Cetus (Cet) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 3.56

Range 3.54 - 3.58

Variable Type Variable (Unclassified)

Spectral Type K1 II + (K)

Star Color Red (B-V 1.22)

Distance 274 ly

2Position & Identifiers

RA 00h 19m 25.7s

Dec -08° 49' 26.0"

Constellation Cetus (Cet)

HR 74

HIP 1562

HD 1522

Bayer Iota

Flamsteed 8 Cet

SIMBAD

3How easy to split?

Primary 3.6 mag Companion 10.4 mag Separation 106.4″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium	Hard+	Hard+
150 mm Newton 150mm Newt.	Easy	Medium+	Medium+
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Medium+

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

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Best season Aug – Oct (peak: Sep)

5Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AC

Separation 106.4″

Companion Mag 10.4

Position Angle 191°

Star Colors A: Red

Discoverer HJ 1953

Notes

Component B, 12.87v at 63", optical.

Separation over time

Measured 1892 → 2014 (122 y)

Separation drift 109.8" → 106.4" (-3.40")

Rate -0.0279" / y

PA drift 198° → 191° (-7°, -0.057°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.