When is the best time to observe 84 Ceti?

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

Where is 84 Ceti located in the sky?

84 Ceti lies in the constellation Cetus at right ascension 02h 41m and declination -00° 42′.

What telescope do I need to split 84 Ceti?

Splitting 84 Ceti requires an aperture of roughly 100 mm or larger — the components are separated by about 3.9″ at magnitudes near 5.7. The companion is about 4.0 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

84 Ceti — Double Star in Cetus

Magnitude 5.7^m DoubleStar Cetus (Cet) Visible

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Observe

1Physical Properties

Magnitude 5.71

Variable Type Delta Scuti (Pulsating)

Spectral Type F7IV subgiant

Star Color Yellow (B-V 0.52)

Distance 91 ly

2Position & Identifiers

RA 02h 41m 13.9s

Dec -00° 41' 45.0"

Constellation Cetus (Cet)

HR 790

HIP 12530

HD 16765

SAO 130055

Flamsteed 84 Cet

Double Cat 2046

SIMBAD

3How easy to split?

Primary 5.7 mag Companion 9.7 mag Separation 3.9″

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

Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Sep – Nov (peak: Oct)

5Multiple Star System

Separation 3.9″

Companion Mag 9.7

Position Angle 301°

Star Colors A: Yellow B: Red

Discoverer STF 295

Separation over time

Measured 1829 → 2022 (193 y)

Separation drift 4.6" → 3.9" (-0.70")

Rate -0.0036" / y

PA drift 335° → 301° (-34°, -0.176°/y)

Slow change over generations — observable in lifetime comparisons.

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.