When is the best time to observe 30 Cygni?

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

Where is 30 Cygni located in the sky?

30 Cygni lies in the constellation Cygnus at right ascension 20h 13m and declination +46° 49′.

What telescope do I need to split 30 Cygni?

Splitting 30 Cygni requires an aperture of roughly 60 mm or larger — the components are separated by about 431.8″ at magnitudes near 4.8. Larger apertures and steady seeing help resolve the pair cleanly.

30 Cygni — Double Star in Cygnus

Observable Double Star Good (54/100)

Sep: 431.8", Companion: mag 7.0

Magnitude 4.8^m DoubleStar Cygnus (Cyg) Visible

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Observe

1Physical Properties

Magnitude 4.83

Variable Type Delta Scuti (Pulsating)

Spectral Type A5IIIn bright giant

Star Color White (B-V 0.09)

Distance 272 ly

2Position & Identifiers

RA 20h 13m 18.0s

Dec +46° 48' 57.0"

Constellation Cygnus (Cyg)

HR 7730

HIP 99639

HD 192514

SAO 49332

Flamsteed 30 Cyg

Double Cat 13554

SIMBAD

3How easy to split?

Primary 4.8 mag Companion 7.0 mag Separation 431.8″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
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)

5Multiple Star System Sextuple B: optical

Components 6 (sextuple)

Component IDs AD

Separation 431.8″

Companion Mag 7.0

Position Angle 150°

Star Colors A: White D: Red

Discoverer GUI 30

Notes

Component D of ADS 13554 of which primary is HR 7735.

Separation over time

Measured 1800 → 2003 (203 y)

Separation drift 432.9" → 431.8" (-1.10")

Rate -0.0054" / y

PA drift 152° → 150° (-2°, -0.010°/y)

Slow change over generations — observable in lifetime comparisons.

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

Telescope Eyepiece

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15x Dawes: 1.9″ TFOV: 3.3°

Seeing

Scale Realistic = true angular size

A: 4.8 · B: 7.0 · Sep: 431.8″ · PA: 150° · 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

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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

Discover

14Stellar Notes

Variable Star

Delta Sct?

Alternative Names

There is very much confusion in the literature as to which of the three stars HR 7730, 7735, 7751 should be called | Omicron1 and which Omricron2: | HR FL SOME BAC Others | 7730 30 Omicron1 Omicron1 - | 7735 31 Omicron2 Omicron2 Omicron1 | 7751 32 - Omicron3 Omicron2 | For these stars, the Greek letter is hence omitted from the Name column.

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