When is the best time to observe Mesarthim?

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

Where is Mesarthim located in the sky?

Mesarthim lies in the constellation Aries at right ascension 01h 54m and declination +19° 18′.

What telescope do I need to split Mesarthim?

Splitting Mesarthim requires an aperture of roughly 80 mm or larger — the components are separated by about 7.3″ at magnitudes near 4.8. Larger apertures and steady seeing help resolve the pair cleanly.

Mesarthim — Double Star in Aries

Gamma2 Ari

Observable Double Star Excellent (74/100)

Sep: 7.3", Companion: mag 4.6

Magnitude 4.8^m DoubleStar Aries (Ari) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.75

Variable Type Alpha2 CVn (Magnetic Rotating)

Spectral Type A1pSi

Star Color White (B-V -0.04)

Distance 125 ly

2Position & Identifiers

RA 01h 53m 31.8s

Dec +19° 17' 37.0"

Constellation Aries (Ari)

HR 546

HIP 8832

HD 11502

SAO 92680

Bayer Gamma2

Flamsteed 5 Ari

Variable ID Gam Ari

Double Cat 1507

SIMBAD Wikipedia

3How easy to split?

Primary 4.8 mag Companion 4.6 mag Separation 7.3″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
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 Sep – Nov (peak: Oct)

5Multiple Star System Triple C: optical

Components 3 (triple)

Component IDs AB

Separation 7.3″

Companion Mag 4.6

Companion Sp B9V

Position Angle 0°

Star Colors A: White B: Blue-white

Discoverer STF 180

Notes

Binary with HR 545, orbital period 5000 - 10000y? Component C, 9.6v at 221". Combined colors for HR 545-6; combined | mag. 3.88V.

Separation over time

Measured 1800 → 2022 (222 y)

Separation drift 8.9" → 7.3" (-1.60")

Rate -0.0072" / y

PA drift 0° → 0° (+0°, +0.000°/y)

Slow change over generations — observable in lifetime comparisons.

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.