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Pi Cephei — Double Star in Cepheus

Observable Double Star Fair (27/100)

Sep: 1.1", Companion: mag 6.8

Magnitude 4.4m DoubleStar Cepheus (Cep) Visible
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1Physical Properties

Magnitude 4.41
Spectral Type G2III giant
Star Color Orange (B-V 0.80)
Distance 544 ly

2Position & Identifiers

RA 23h 07m 53.9s
Dec +75° 23' 15.0"
Constellation Cepheus (Cep)
HR 8819
HIP 114222
HD 218658
SAO 10629
Bayer Pi
Flamsteed 33 Cep
Double Cat 16538
SIMBAD

3How easy to split?

Primary 4.4 mag Companion 6.8 mag Separation 1.2″
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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. V. hard+ V. hard+ V. hard+
150mm Newt. Hard Hard Hard
C8 203mm Hard+ Hard+ Hard+
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 230 mm reflector.

4Visibility

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Best season Aug – Oct (peak: Sep)

5Multiple Star System Triple

Components 3 (triple)
Component IDs AB
Separation 1.1″
Companion Mag 6.8
Position Angle 3°
Star Colors A: Orange B: Red
Discoverer STT 489
AB 4.6 G2III, 6.6 F3V, 150y, a = 0.86". Combined mag., colors. Companion may be collapsed star.

Separation over time

Period: 176.0 y Eccentricity: 0.661 Now: 1.2", PA 6° + 0.01" in 5 years
0.00" 0.33" 0.67" 1.00" 1.3" 2025 2030 2035 2040 2045 1.2"

Apparent separation over time, computed from ORB6 orbital elements. Steep curves indicate fast-changing pairs — catch them while they're splittable.

Eyepiece View

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80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E

A: 4.4 · B: 6.8 · Sep: 1.1″ · PA: 3° · N up, E right

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

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7

Size Comparison

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8

Compare Stars

9

Spectral Classification

10

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map
11

Stellar Lifecycle

12

Blackbody Spectrum

13

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

14

Stellar Fusion

Discover

15Stellar Notes

ADS 16538A, 556.2d, K 23.0k/s, V0 -19.6k/s, asini 169.
0.020".
16

Light Travel Time Machine

17

Relativistic Travel

Nearby in the Sky

Other targets within a few degrees — pan your scope a little and keep exploring.

Visibility scores assume a 150 mm Newton at Bortle 4.

21 Cas
Hard+
Eclipsing binary, period 4.5d
Variable Star mag 5.66 6.2° Cassiopeia
34 Cep
Easy
Easy double, sep 3.5″
Double Star mag 4.75 7.3° Cepheus
NGC 7762
Easy
Open cluster
Open Cluster mag 10.0 8.0° Cepheus
Alfirk
HIP 106032; Beta Cephei; 8 Cephei
Easy
Hot blue O-type star
Double Star mag 3.23 8.6° Cepheus
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