When is the best time to observe 59 Cygni?

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

Where is 59 Cygni located in the sky?

59 Cygni lies in the constellation Cygnus at right ascension 20h 60m and declination +47° 31′.

What telescope do I need to split 59 Cygni?

Splitting 59 Cygni requires an aperture of roughly 60 mm or larger — the components are separated by about 21.0″ at magnitudes near 4.7. The companion is about 4.7 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

59 Cygni — Double Star in Cygnus

Magnitude 4.5–4.9^m DoubleStar Cygnus (Cyg) Visible

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1Physical Properties

Magnitude 4.74

Range 4.49 - 5.07

Period 28.2 days

Variable Type Gamma Cassiopeiae (Eruptive Be Star)

Spectral Type B1ne

Star Color Blue (B-V -0.05)

2Position & Identifiers

RA 20h 59m 49.6s

Dec +47° 31' 16.0"

Constellation Cygnus (Cyg)

HR 8047

HIP 103632

HD 200120

SAO 50335

Flamsteed 59 Cyg

Variable ID V832 Cyg

Double Cat 14526

SIMBAD

3How easy to split?

Primary 4.7 mag Companion 9.4 mag Separation 21.0″

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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 Jun – Aug (peak: Jul)

5Light Curve

6Multiple Star System Quadruple D,E: optical

Components 4 (quadruple)

Component IDs AB

Separation 21.0″

Companion Mag 9.4

Position Angle 353°

Star Colors A: Blue B: Yellow-white

Discoverer STF2743

Notes

AB CPM. B, 9.38V, +0.22(B-V), +0.04(U-B) A8III, vsini 97k/s. Component C, 12v at 26" optical.

Separation over time

Measured 1828 → 2012 (184 y)

Separation drift 16.0" → 21.0" (+5.00")

Rate +0.0272" / y

PA drift 352° → 353° (+1°, +0.005°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

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

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.7 · B: 9.4 · Sep: 21.0″ · PA: 353° · N up, E right

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

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Size Comparison

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Spectral Classification

10

Hertzsprung-Russell Diagram

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Stellar Lifecycle

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Blackbody Spectrum

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Stellar Absorption Spectrum

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Stellar Fusion

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15Stellar Notes

Variable Star

ADS 14526A, Gamma Cas 4.49 - 4.88V. Expanding circumstellar shell. Marked evidence of mass loss. Shell spectrum faded | between 1973 and 1975. Metallic absorption lines disappeared.

Group/Cluster

Cyg OB7.

Spectral

Ultraviolet envelope. Variously classified O9V, B0p, B1IV:e, B1.5Venn, B3ne. Component B, A3V.