When is the best time to observe Eta Crucis?

Eta Crucis is best observed from February through April, with peak visibility during March when it transits around midnight in the Northern Hemisphere.

Where is Eta Crucis located in the sky?

Eta Crucis lies in the constellation Crux at right ascension 12h 07m and declination -64° 37′.

What telescope do I need to split Eta Crucis?

Splitting Eta Crucis requires an aperture of roughly 60 mm or larger — the components are separated by about 48.8″ at magnitudes near 4.2. The companion is about 7.7 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Eta Crucis — Double Star in Crux

Magnitude 4.2^m DoubleStar Crux (Cru) Visible

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Observe

1Physical Properties

Magnitude 4.15

Spectral Type F2III giant

Star Color Yellow-white (B-V 0.34)

Distance 62 ly

2Position & Identifiers

RA 12h 06m 52.9s

Dec -64° 36' 49.0"

Constellation Crux (Cru)

HR 4616

HIP 59072

HD 105211

SAO 251742

Bayer Eta

SIMBAD

3How easy to split?

Primary 4.2 mag Companion 11.8 mag Separation 48.8″

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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 Feb – Apr (peak: Mar)

5Multiple Star System C: optical

Separation 48.8″

Companion Mag 11.8

Position Angle 300°

Star Colors A: Yellow-white

Discoverer HJ 4501

Separation over time

Measured 1835 → 2015 (180 y)

Separation drift 30.0" → 48.8" (+18.80")

Rate +0.1044" / y

PA drift 298° → 300° (+2°, +0.011°/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.