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Eta Coronae Borealis — Double Star in Corona Borealis

HIP 75312; Eta Coronae Borealis; 2 Coronae Borealis

Magnitude 5.6m DoubleStar Corona Borealis (CrB) Visible
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1Physical Properties

Magnitude 5.58
Spectral Type G0V
Star Color Yellow (B-V 0.58)
Distance 53 ly

2Position & Identifiers

RA 15h 23m 12.3s
Dec +30° 17' 16.0"
Constellation Corona Borealis (CrB)
HR 5727
HIP 75312
HD 137107
SAO 64673
Bayer Eta
Flamsteed 2 CrB
Double Cat 9617
SIMBAD Wikipedia

3How easy to split?

Primary 5.6 mag Companion 6.0 mag Separation 0.8″
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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 280 mm reflector.

4Visibility

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Best season Apr – Jun (peak: May)

5Multiple Star System Quadruple

Components 4 (quadruple)
Component IDs AB
Separation 0.8″
Companion Mag 6.0
Companion Sp G0V
Position Angle 356°
Star Colors A: Yellow B: Yellow
Discoverer STF1937
AB 5.62 G1V, 5.89 G3V, 41.623y, a = 0.907". B is HR 5728. Colors for combined images. Mag. for blend 4.98V. Masses | 0.95 and 0.94 solar. C, 13.4v at 58" optical; D, 11v at 215" probably optical.

Separation over time

Period: 14.3 y Eccentricity: 0.279 Now: 0.78", PA 60° -0.11" in 5 years
0.00" 0.30" 0.60" 0.90" 1.2" 2022 2025 2028 2031 0.78"

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 356°

A: 5.6 · B: 6.0 · Sep: 0.8″ · PA: 356° · 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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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

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14Stellar Notes

Blend of 5727/8, 4.94 - 5.02V. Uncertain which component is the variable.
ADS 9617A, 41.56y D, K 4.5k/s, V0 -6.0k/s, asini 904.
UMa cluster; Sirius group? UMa stream.
0.054".
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.

Delta Boo
Easy
Easy double, sep 104.7″
Double Star mag 3.47 3.4° Boötes
Blaze Star
HR 5958
Medium+
Mira-type variable, range 2.0–10.8
Variable Star mag 10.00 9.1° Corona Borealis
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