When is the best time to observe Mu Cygni?

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

Where is Mu Cygni located in the sky?

Mu Cygni lies in the constellation Cygnus at right ascension 21h 44m and declination +28° 45′.

What telescope do I need to split Mu Cygni?

Splitting Mu Cygni requires an aperture of roughly 150 mm or larger — the components are separated by about 1.4″ at magnitudes near 4.7. Larger apertures and steady seeing help resolve the pair cleanly.

Mu Cygni — Double Star in Cygnus

Mu Cyg (BS8309)

Observable Double Star Fair (28/100)

Sep: 1.4", Companion: mag 6.2

Magnitude 4.7^m DoubleStar Cygnus (Cyg) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.73

Spectral Type F6V

Star Color Yellow (B-V 0.48)

Distance 67 ly

2Position & Identifiers

RA 21h 44m 08.6s

Dec +28° 44' 34.0"

Constellation Cygnus (Cyg)

HR 8309

HIP 107310

HD 206826

SAO 89940

Bayer Mu

Flamsteed 78 Cyg

Double Cat 15270

SIMBAD Wikipedia

3How easy to split?

Primary 4.7 mag Companion 6.2 mag Separation 1.4″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	V. hard+	V. hard+	V. hard+
150 mm Newton 150mm Newt.	Hard+	Hard+	Hard+
Celestron C8 (203 mm SCT) C8 203mm	Medium	Medium	Medium

Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Jul – Sep (peak: Aug)

5Multiple Star System Quintuple C,D,F,G: optical

Components 5 (quintuple)

Component IDs AB

Separation 1.4″

Companion Mag 6.2

Companion Sp G2V

Position Angle 325°

Star Colors A: Yellow B: Yellow

Discoverer STF2822

Notes

AB 4.78 F4V, 6.09 G2V, 507.5y, a = 4.278". B is HR 8310. Combined colors. Mag. for blend 4.50V. Components C, D, | optical. D, at 201" is ADS 15275, 6.9 A5, 13.3v sep. 16".