When is the best time to observe Mirach?

Mirach is best observed from September through November, with peak visibility during October when it transits around midnight in the Northern Hemisphere.

Where is Mirach located in the sky?

Mirach lies in the constellation Andromeda at right ascension 01h 10m and declination +35° 37′.

What telescope do I need to split Mirach?

Splitting Mirach requires an aperture of roughly 60 mm or larger — the components are separated by about 65.3″ at magnitudes near 2.1. The companion is about 9.7 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Mirach — Double Star in Andromeda

Beta And

DoubleStar Andromeda (And) Visible 1 Exoplanet

Star Map + List + Plan

About Mirach

Description

Mirach is a red giant of spectral type M0IIIa at magnitude 2.06 in Andromeda. Located about 197 light-years from Earth, it has a luminosity of roughly 1,900 times solar and a diameter about 100 times the Sun's. Its warm reddish-orange color is easily noticeable to the naked eye.

Observing Tips

Mirach is the middle of the three bright stars forming the main chain of Andromeda, northeast of the Great Square of Pegasus. It is a useful guide to M31 — the Andromeda Galaxy lies about 8 degrees northwest of Mirach, found by turning right from the Mirach-Mu And line. Its distinctive red-orange color helps identify it. Best observed September through January.

History

The name Mirach derives from the Arabic 'mi'zar,' meaning 'the girdle' or 'waistcloth.' In some traditions it was called 'the Belt of Andromeda.' Mirach has been a key guide star for finding the Andromeda Galaxy since the earliest days of deep-sky astronomy.

Fun Facts

Mirach has a small galaxy (NGC 404, nicknamed 'Mirach's Ghost') just 7 arcminutes away, easily visible in a small telescope. The glow of Mirach makes this faint galaxy hard to spot, giving it its ghostly nickname.

Observe

1Physical Properties

Magnitude 2.06

Range 2.01 - 2.1

Variable Type Slow Irregular Variable

Spectral Type M0+ IIIa

Star Color Red (B-V 1.58)

Distance 197 ly

2Position & Identifiers

RA 01h 09m 43.9s

Dec +35° 37' 14.0"

Constellation Andromeda (And)

HR 337

HIP 5447

HD 6860

Bayer Beta

Flamsteed 43 And

Double Cat 949

SIMBAD Wikipedia

3How easy to split?

Primary 2.1 mag Companion 11.8 mag Separation 65.3″

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

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

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Best season Sep – Nov (peak: Oct)

5Multiple Star System Quintuple B,C,D: optical

Components 5 (quintuple)

Component IDs AD

Separation 65.3″

Companion Mag 11.8

Companion Sp IIIa

Position Angle 149°

Star Colors A: Red

Discoverer BAR 1

Separation over time

Measured 1879 → 2015 (136 y)

Separation drift 90.8" → 65.3" (-25.50")

Rate -0.1875" / y

PA drift 141° → 149° (+8°, +0.059°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

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.