When is the best time to observe R Cassiopeiae?

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

Where is R Cassiopeiae located in the sky?

R Cassiopeiae lies in the constellation Cassiopeia at right ascension 23h 58m and declination +51° 23′.

What telescope do I need to follow R Cassiopeiae?

To follow R Cassiopeiae through its full brightness cycle (magnitude 4.7 to 13.5) you need a telescope of roughly 290 mm or larger — the star fades out of smaller apertures near minimum light.

R Cassiopeiae — Variable Star in Cassiopeia

Observable Variable Star Showpiece (78/100)

Range: 4.7 - 13.5, Period: 430.0d, Type: M

Magnitude 4.7–13.5^m VariableStar Cassiopeia (Cas) Visible

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1Physical Properties

Magnitude 4.80

Range 4.7 - 13.5

Period 430 days

Variable Type Mira (Long-period Pulsating)

Spectral Type M7IIIe bright giant

Star Color Deep ruby red (B-V 1.83)

2Position & Identifiers

RA 23h 58m 24.8s

Dec +51° 23' 19.0"

Constellation Cassiopeia (Cas)

HR 9066

HIP 118188

HD 224490

SAO 35938

Variable ID R Cas

Double Cat 17135

SIMBAD

3How easy to follow?

Magnitude 4.7 – 13.5 mag Amplitude 8.8 mag Period 430 d Type M

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Equipment	Bortle 3	Bortle 4	Bortle 5
Naked eye Naked eye	Imp.	Imp.	Imp.
50 mm finder 50mm finder	Imp.	Imp.	Imp.
150 mm telescope 150mm scope	V. hard+	V. hard	V. hard

Easy Medium Hard Very hard Impossible

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

To reach "Medium" at Bortle 3, you'd need at least a 290 mm reflector.

4Visibility

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Best season Aug – Oct (peak: Sep)

5Survey Image

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6Light Curve

7Comparison Stars for R Cas (4.7–13.5)

Nearby stable stars for estimating brightness (AAVSO)

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8

Size Comparison

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9

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10

Spectral Classification

11

Hertzsprung-Russell Diagram

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12

Stellar Lifecycle

13

Blackbody Spectrum

14

Stellar Absorption Spectrum

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

15

Stellar Fusion

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16Stellar Notes

Variable Star

ADS 17135A, M 4.7 - 13.5v, 430.46d. Variable SiO maser source, indicating shell-like structure. Single cycle 6.45 to | 11.25V, +1.31 to +2.66(B-V), -0.07 to +1.02(U-B).

Double Star

Companions optical.

Spectral

OH and H2O emission strong in infrared. IR spectra show water vapor. Variable M6e-M10e.