When is the best time to observe Sigma Cassiopeiae?

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

Where is Sigma Cassiopeiae located in the sky?

Sigma Cassiopeiae lies in the constellation Cassiopeia at right ascension 23h 59m and declination +55° 45′.

What telescope do I need to split Sigma Cassiopeiae?

Splitting Sigma Cassiopeiae requires an aperture of roughly 100 mm or larger — the components are separated by about 3.1″ at magnitudes near 4.9. Larger apertures and steady seeing help resolve the pair cleanly.

Sigma Cassiopeiae — Double Star in Cassiopeia

Observable Double Star Excellent (60/100)

Sep: 3.1", Companion: mag 7.2

Magnitude 4.9^m DoubleStar Cassiopeia (Cas) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.88

Spectral Type B1V

Star Color Blue (B-V -0.07)

Distance 544 ly

2Position & Identifiers

RA 23h 59m 00.5s

Dec +55° 45' 18.0"

Constellation Cassiopeia (Cas)

HR 9071

HIP 118243

HD 224572

SAO 35947

Bayer Sigma

Flamsteed 8 Cas

Double Cat 17140

SIMBAD

3How easy to split?

Primary 4.9 mag Companion 7.2 mag Separation 3.1″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium	Medium	Medium
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 Aug – Oct (peak: Sep)

5Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AB

Separation 3.1″

Companion Mag 7.2

Position Angle 326°

Star Colors A: Blue B: Yellow-white

Discoverer STF3049

Notes

AB binary, 5.0v B2III, 7.1v B3V.

Separation over time

Measured 1823 → 2021 (198 y)

Separation drift 2.9" → 3.1" (+0.20")

Rate +0.0010" / y

PA drift 328° → 326° (-2°, -0.010°/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.