When is the best time to observe AR Cassiopeiae?

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

Where is AR Cassiopeiae located in the sky?

AR Cassiopeiae lies in the constellation Cassiopeia at right ascension 23h 30m and declination +58° 33′.

What telescope do I need to split AR Cassiopeiae?

Splitting AR Cassiopeiae requires an aperture of roughly 60 mm or larger — the components are separated by about 75.0″ at magnitudes near 4.9. Larger apertures and steady seeing help resolve the pair cleanly.

AR Cassiopeiae — Double Star in Cassiopeia

Observable Double Star Excellent (62/100)

Sep: 75.0", Companion: mag 7.2

DoubleStar Cassiopeia (Cas) Visible

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Observe

1Physical Properties

Magnitude 4.91

Range 4.82 - 4.96

Period 6.1 days

Variable Type Eclipsing Binary (Algol-type)

Spectral Type B3IV

Star Color Blue-white (B-V -0.12)

Distance 544 ly

2Position & Identifiers

RA 23h 30m 02.0s

Dec +58° 32' 56.0"

Constellation Cassiopeia (Cas)

HR 8926

HIP 115990

HD 221253

Variable ID AR Cas

Double Cat 16795

SIMBAD

3How easy to split?

Primary 4.9 mag Companion 7.2 mag Separation 75.0″

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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 Aug – Oct (peak: Sep)

5Light Curve

6Multiple Star System 8 components

Components 8

Component IDs AC

Separation 75.0″

Companion Mag 7.2

Position Angle 269°

Star Colors A: Blue-white C: Yellow

Discoverer SHJ 355

Notes

AB, 4.9, 9.3V, 1500y, sep. 1.1". CD, 8.2 A0Vn, 9.8v, sep. 1.6"; vsini of C, 210k/s. Component E, optical.

Separation over time

Measured 1800 → 2018 (218 y)

Separation drift 75.8" → 75.0" (-0.80")

Rate -0.0037" / y

PA drift 270° → 269° (-1°, -0.005°/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.

Eyepiece View

Telescope Eyepiece

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.9 · B: 7.2 · Sep: 75.0″ · PA: 269° · N up, E left

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″

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Size Comparison

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Compare Stars

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Spectral Classification

10

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map

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Stellar Lifecycle

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Blackbody Spectrum

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Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

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Stellar Fusion

Discover

15Stellar Notes

Variable Star

ADS 16795A, EA 4.84 - 4.98V, 6.0663309d; i 90d.

Spectroscopic Binary

ADS 16795A, 6.0663d, K 56.7k/s, V0 -13.4k/s, asini 4.58. Alternate orbits 6.0663309d, K 54.18k/s, V0 -10.10k/s, | asini 4.44; 6.0668d, K 56.2k/s, V0 -11.0k/s, asini 4.6027. Apsidal period 1500 1800y.

Group/Cluster

Cas-Tau OB1.

Dynamical

0.003" for components CD.

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