When is the best time to observe T Cygni?

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

Where is T Cygni located in the sky?

T Cygni lies in the constellation Cygnus at right ascension 20h 47m and declination +34° 22′.

What telescope do I need to split T Cygni?

Splitting T Cygni requires an aperture of roughly 60 mm or larger — the components are separated by about 10.0″ at magnitudes near 4.9. The companion is about 5.1 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

T Cygni — Double Star in Cygnus

Magnitude 4.9^m DoubleStar Cygnus (Cyg) Visible

Star Map + List + Plan

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1Physical Properties

Magnitude 4.92

Range 4.91 - 4.96

Variable Type LB:

Spectral Type K3III giant

Star Color Red (B-V 1.32)

Distance 652 ly

2Position & Identifiers

RA 20h 47m 10.8s

Dec +34° 22' 27.0"

Constellation Cygnus (Cyg)

HR 7956

HIP 102571

HD 198134

SAO 70499

Variable ID T Cyg

Double Cat 14290

SIMBAD

3How easy to split?

Primary 4.9 mag Companion 10.0 mag Separation 10.0″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium	Medium	Hard+
150 mm Newton 150mm Newt.	Easy	Easy	Medium+
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

Set a location in User Settings to see visibility data.

Best season Jun – Aug (peak: Jul)

5Multiple Star System Triple

Components 3 (triple)

Component IDs AB

Separation 10.0″

Companion Mag 10.0

Position Angle 120°

Star Colors A: Red

Discoverer BU 677

Notes

AB CPM. B, 10.03V, +1.27(B-V), +0.66(U-B). C, 13v at 14" optical.

Separation over time

Measured 1877 → 2016 (139 y)

Separation drift 10.0" → 10.0" (+0.00")

Rate +0.0000" / y

PA drift 121° → 120° (-1°, -0.007°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

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.