When is the best time to observe 81 Tauri?

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

Where is 81 Tauri located in the sky?

81 Tauri lies in the constellation Taurus at right ascension 04h 31m and declination +15° 42′.

What telescope do I need to split 81 Tauri?

Splitting 81 Tauri requires an aperture of roughly 60 mm or larger — the components are separated by about 162.3″ at magnitudes near 5.5. The companion is about 3.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

81 Tauri — Double Star in Taurus

Observable Double Star Good (41/100)

Sep: 162.3", Companion: mag 8.9

Magnitude 5.5^m DoubleStar Taurus (Tau) Visible

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Observe

1Physical Properties

Magnitude 5.48

Spectral Type A5m

Star Color Yellow-white (B-V 0.26)

2Position & Identifiers

RA 04h 30m 38.9s

Dec +15° 41' 31.0"

Constellation Taurus (Tau)

HR 1428

HIP 21039

HD 28546

SAO 93978

Flamsteed 81 Tau

SIMBAD

3How easy to split?

Primary 5.5 mag Companion 8.9 mag Separation 162.3″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Medium+	Medium+
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 Oct – Dec (peak: Nov)

5Multiple Star System

Separation 162.3″

Companion Mag 8.9

Position Angle 339°

Star Colors A: Yellow-white B: Orange

Discoverer BUP 62

Separation over time

Measured 1904 → 2015 (111 y)

Separation drift 161.8" → 162.3" (+0.50")

Rate +0.0045" / y

PA drift 339° → 339° (+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.