When is the best time to observe Aldebaran?

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

Where is Aldebaran located in the sky?

Aldebaran lies in the constellation Taurus at right ascension 04h 36m and declination +16° 31′.

What telescope do I need to split Aldebaran?

Splitting Aldebaran requires an aperture of roughly 60 mm or larger — the components are separated by about 136.3″ at magnitudes near 0.8. The companion is about 10.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Aldebaran — Double Star in Taurus

HIP 21421; Alpha Tauri; 87 Tauri

DoubleStar Taurus (Tau) Visible 1 Exoplanet

Star Map + List + Plan

About Aldebaran

Description

Aldebaran is an orange giant of spectral type K5III at magnitude 0.85, the brightest star in Taurus and the 14th brightest in the sky. Located about 65 light-years from Earth, it has a luminosity of roughly 425 times solar and a diameter about 44 times that of the Sun. Despite appearing to be part of the Hyades star cluster, Aldebaran is actually in the foreground at less than half the cluster's distance.

Observing Tips

Aldebaran is easy to find by following Orion's Belt to the upper-right (northwest). It appears as the bright orange 'eye' of the Bull, embedded in the V-shaped Hyades cluster. Its deep orange color is beautiful in binoculars. The Moon regularly occults Aldebaran, creating a dramatic event visible in small telescopes. Best observed November through March.

History

The name Aldebaran comes from the Arabic 'al-dabaran,' meaning 'the follower,' because it appears to follow the Pleiades across the sky. It has been recognized as the Bull's eye since Babylonian times. Aldebaran was one of the four Royal Stars of Persia around 3000 BC, serving as a marker of the vernal equinox.

Fun Facts

Pioneer 10, the first spacecraft to leave the solar system, is heading in the general direction of Aldebaran and will make its closest approach in about 2 million years. As a foreground star, Aldebaran is not a member of the Hyades — it merely lies along the same line of sight by coincidence.

Observe

1Physical Properties

Magnitude 0.85

Range 0.86 - 0.89

Variable Type LB:

Spectral Type K5III

Star Color Red (B-V 1.54)

Temperature 3881 K

Radius 44.3 R☉

Distance 65 ly

2Position & Identifiers

RA 04h 35m 55.2s

Dec +16° 30' 33.0"

Constellation Taurus (Tau)

HR 1457

HIP 21421

HD 29139

Bayer Alpha

Flamsteed 87 Tau

Variable ID Alp Tau

Double Cat 3321

SIMBAD Wikipedia

3How easy to split?

Primary 0.9 mag Companion 11.3 mag Separation 136.3″

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

Easy Medium Hard Very hard Impossible

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

4Visibility

Set a location in User Settings to see visibility data.

Best season Oct – Dec (peak: Nov)

5Multiple Star System Sextuple C: optical

Components 6 (sextuple)

Component IDs AC

Separation 136.3″

Companion Mag 11.3

Companion Sp M2

Position Angle 32°

Star Colors A: Red C: Red

Discoverer STFB 2

Notes

AB binary. B is 13.5v, dM2 at 31". CD, 122" from A is 11.2, 13.6v sep. 2" also binary but independent of AB.

Separation over time

Measured 1781 → 2023 (242 y)

Separation drift 87.8" → 136.3" (+48.50")

Rate +0.2004" / y

PA drift 37° → 32° (-5°, -0.021°/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.