When is the best time to observe 55 Eridani?

55 Eridani is best observed from October through December, with peak visibility during November when it transits around midnight in the Northern Hemisphere.

Where is 55 Eridani located in the sky?

55 Eridani lies in the constellation Eridanus at right ascension 04h 44m and declination -08° 48′.

What telescope do I need to split 55 Eridani?

Splitting 55 Eridani requires an aperture of roughly 80 mm or larger — the components are separated by about 9.3″ at magnitudes near 6.7. Larger apertures and steady seeing help resolve the pair cleanly.

55 Eridani — Double Star in Eridanus

Magnitude 6.7^m DoubleStar Eridanus (Eri) Visible

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Observe

1Physical Properties

Magnitude 6.70

Spectral Type G8III giant

Star Color Orange (B-V 0.92)

Distance 408 ly

2Position & Identifiers

RA 04h 43m 35.1s

Dec -08° 47' 46.0"

Constellation Eridanus (Eri)

HR 1506

HIP 21986

HD 30020

SAO 131442

Flamsteed 55 Eri

Double Cat 3409

SIMBAD

3How easy to split?

Primary 6.7 mag Companion 6.8 mag Separation 9.3″

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

Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Oct – Dec (peak: Nov)

5Multiple Star System

Separation 9.3″

Companion Mag 6.8

Position Angle 318°

Star Colors A: Orange B: Yellow-white

Discoverer STF 590

Notes

CPM with HR 1505.

Separation over time

Measured 1783 → 2018 (235 y)

Separation drift 9.2" → 9.3" (+0.10")

Rate +0.0004" / y

PA drift 314° → 318° (+4°, +0.017°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

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.