Rho Capricorni — Double Star in Capricornus

Observable Double Star Fair (26/100)

Sep: 1.9", Companion: mag 6.7

Magnitude 4.8^m DoubleStar Capricornus (Cap) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.78

Spectral Type F2IV subgiant

Star Color Yellow-white (B-V 0.38)

Distance 69 ly

2Position & Identifiers

RA 20h 28m 51.6s

Dec -17° 48' 49.0"

Constellation Capricornus (Cap)

HR 7822

HIP 101027

HD 194943

SAO 163614

Bayer Rho

Flamsteed 11 Cap

Double Cat 13887

3How easy to split?

Primary 4.8 mag Companion 6.7 mag Separation 1.9″

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

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Best season Jun – Aug (peak: Jul)

5Multiple Star System Quintuple C,D: optical

Components 5 (quintuple)

Component IDs AD

Separation 1.9″

Companion Mag 6.7

Position Angle 150°

Star Colors A: Yellow-white D: Yellow

Discoverer SHJ 323

Notes

AB binary. B, 8.0v at 0.8".

Separation over time

Period: 346.6 y Eccentricity: 0.959 Now: 1.9", PA 188° + 0.10" in 5 years

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

Eyepiece View

Telescope Eyepiece

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.8 · B: 6.7 · Sep: 1.9″ · PA: 150° · N up, E right

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

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6

Size Comparison

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7

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8

Spectral Classification

9

Hertzsprung-Russell Diagram

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

10

Stellar Lifecycle

11

Blackbody Spectrum

12

Stellar Absorption Spectrum

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

13

Stellar Fusion

Discover

14Stellar Notes

Group/Cluster

Sirius group.

Dynamical

0.017".

15

Light Travel Time Machine

16

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.

Easy double, sep 3.5″

Double Star mag 5.25 0.5° Capricornus

Easy double, sep 22.0″

Double Star mag 5.94 0.8° Capricornus

Elliptical galaxy

Galaxy mag 13.0 1.9° Capricornus

HIP 100345; Beta Capricorni; 9 Capricorni

Colorful double, sep 205.2″

Double Star mag 3.08 3.6° Capricornus

Compact globular cluster

Globular Cluster mag 8.6 6.7° Sagittarius

Semi-regular variable, range 6.2–6.5

Variable Star mag 6.34 8.5° Aquila

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