When is the best time to observe Mu Orionis?

Mu Orionis is best observed from November through January, with peak visibility during December when it transits around midnight in the Northern Hemisphere.

Where is Mu Orionis located in the sky?

Mu Orionis lies in the constellation Orion at right ascension 06h 02m and declination +09° 39′.

What telescope do I need to split Mu Orionis?

Splitting Mu Orionis requires an aperture of roughly 670 mm or larger — the components are separated by about 0.3″ at magnitudes near 4.1. Larger apertures and steady seeing help resolve the pair cleanly.

Mu Orionis — Double Star in Orion

Magnitude 4.1^m DoubleStar Orion (Ori) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.12

Variable Type Alpha2 CVn (Magnetic Rotating)

Spectral Type A2V

Star Color White (B-V 0.16)

Distance 116 ly

2Position & Identifiers

RA 06h 02m 23.0s

Dec +09° 38' 51.0"

Constellation Orion (Ori)

HR 2124

HIP 28614

HD 40932

SAO 113389

Bayer Mu

Flamsteed 61 Ori

Double Cat 4617

SIMBAD

3How easy to split?

Primary 4.1 mag Companion 6.3 mag Separation 0.4″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	V. hard	V. hard	V. hard
150 mm Newton 150mm Newt.	V. hard	V. hard	V. hard
Celestron C8 (203 mm SCT) C8 203mm	V. hard	V. hard	V. 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 670 mm reflector.

4Visibility

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Best season Nov – Jan (peak: Dec)

5Multiple Star System Triple

Components 3 (triple)

Component IDs AB

Separation 0.3″

Companion Mag 6.3

Position Angle 32°

Star Colors A: White B: Yellow

Discoverer A 2715

Notes

AB 4.4 A2V, 6.0 F3V, 17.5d, a = 0.276"; ABxP, 18.25y, a = 0.089". Magnitude and colors for combined light. A is alpha | CVn var., SB1, 4.45d; B is SB2, 4.78d. Component C, 14v at 18" probably optical.

Separation over time

Period: 18.6 y Eccentricity: 0.744 Now: 0.36", PA 24° + 0.03" 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: 4.1 · B: 6.3 · Sep: 0.3″ · PA: 32° · N up, E right

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

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Size Comparison

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Compare Stars

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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

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15Stellar Notes

Variable Star

ADS 4617A, Alpha CV 4.10 - 4.18V.

Spectroscopic Binary

ADS 4617A, 4.4476d, K 28.4k/s, V0 var., asini 1.74. Alternate orbit 4.4478d, K 29.2k/s, V0 +40.9k/s, | asini 1.79. Speckle interferometric sep. 0.153" 1980.94; unresolved 1983.94. ADS 4617AB, 18y, K 14.9k/s, | V0 +43.3k/s, asini 851. ADS 4617B is SB2, 4.78d.

Group/Cluster

Mel 25; the Hyades.

Spectral

K/m indicate A3/A7, respectively.

Dynamical

0.023".

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