When is the best time to observe Eta Leonis?

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

Where is Eta Leonis located in the sky?

Eta Leonis lies in the constellation Leo at right ascension 10h 07m and declination +16° 46′.

What telescope do I need to split Eta Leonis?

Splitting Eta Leonis requires an aperture beyond typical amateur scopes — even 500 mm struggles against the primary's glare — the components are separated by about 0.4″ at magnitudes near 3.5. The companion is about 4.9 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Eta Leonis — Double Star in Leo

Magnitude 3.5^m DoubleStar Leo Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 3.52

Range 3.49 - 3.53

Variable Type ACYG

Spectral Type A0Ib supergiant

Star Color Blue-white (B-V -0.03)

Distance 1,263 ly

2Position & Identifiers

RA 10h 07m 20.0s

Dec +16° 45' 46.0"

Constellation Leo

HR 3975

HIP 49583

HD 87737

SAO 98955

Bayer Eta

Flamsteed 30 Leo

SIMBAD

3How easy to split?

Primary 3.5 mag Companion 8.4 mag Separation 0.4″

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

Easy Medium Hard Very hard Impossible

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

Out of reach for typical amateur telescopes, even at Bortle 3.

4Visibility

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Best season Jan – Mar (peak: Feb)

5Multiple Star System

Separation 0.4″

Companion Mag 8.4

Position Angle 239°

Star Colors A: Blue-white

Discoverer WRH 18

Notes

Binary, sep. 0.097", unresolved by speckle interferometry 1982.17.

Separation over time

Measured 1937 → 2015 (78 y)

Separation drift 0.10" → 0.40" (+0.30")

Rate +0.0038" / y

PA drift 84° → 239° (+155°, +1.987°/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.