When is the best time to observe Chi Cygni?

Chi Cygni is best observed from June through August, with peak visibility during July when it transits around midnight in the Northern Hemisphere.

Where is Chi Cygni located in the sky?

Chi Cygni lies in the constellation Cygnus at right ascension 19h 51m and declination +32° 55′.

What telescope do I need to follow Chi Cygni?

To follow Chi Cygni through its full brightness cycle (magnitude 3.3 to 14.2) you need a telescope of roughly 390 mm or larger — the star fades out of smaller apertures near minimum light.

Chi Cygni — Variable Star in Cygnus

Observable Variable Star Showpiece (80/100)

Range: 3.3 - 14.2, Period: 408.0d, Type: M

Magnitude 3.3–14.2^m VariableStar Cygnus (Cyg) Visible

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1Physical Properties

Magnitude 4.23

Range 3.3 - 14.2

Period 408 days

Variable Type Mira (Long-period Pulsating)

Spectral Type S6+/1e

Star Color Deep ruby red (B-V 1.82)

Distance 272 ly

2Position & Identifiers

RA 19h 50m 33.9s

Dec +32° 54' 51.0"

Constellation Cygnus (Cyg)

HR 7564

HIP 97629

HD 187796

SAO 68943

Bayer Chi

Variable ID Chi Cyg

SIMBAD

3How easy to follow?

Magnitude 3.3 – 14.2 mag Amplitude 10.9 mag Period 408 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	Imp.	Imp.

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 390 mm reflector.

4Visibility

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Best season Jun – Aug (peak: Jul)

5Survey Image

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6Light Curve

7Comparison Stars for Chi Cyg (3.3–14.2)

Nearby stable stars for estimating brightness (AAVSO)

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Size Comparison

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Spectral Classification

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Hertzsprung-Russell Diagram

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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

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17Stellar Notes

Variable Star

Discovered by Kirch in 1686. M 3.3 - 14.2v. Period changes: 1686-1842, 405.88d; subsequently 408.05d. | Variable CO emission from circumstellar envelope and enhancement of shell at minimum light. Total visual absorption of | shell = 2 mag. Variable SiO maser source. Appreciable reddening at ascending light.

Spectral

Probable SiO maser emission. Most intense infrared CO bands observed in any star to 1973. Technetium found in | spectrum. Also classified S6,2e-S10,4e.

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