When is the best time to observe Chi Geminorum?

Chi Geminorum is best observed from December through February, with peak visibility during January when it transits around midnight in the Northern Hemisphere.

Where is Chi Geminorum located in the sky?

Chi Geminorum lies in the constellation Gemini at right ascension 08h 04m and declination +27° 48′.

What telescope do I need to split Chi Geminorum?

Splitting Chi Geminorum requires an aperture of roughly 60 mm or larger — the components are separated by about 83.6″ at magnitudes near 4.9. The companion is about 6.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Chi Geminorum — Double Star in Gemini

DoubleStar Gemini (Gem) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.94

Spectral Type K1.5III

Star Color Orange (B-V 1.12)

Distance 204 ly

2Position & Identifiers

RA 08h 03m 31.1s

Dec +27° 47' 39.0"

Constellation Gemini (Gem)

HR 3149

HIP 39424

HD 66216

Bayer Chi

SIMBAD

3How easy to split?

Primary 4.9 mag Companion 11.5 mag Separation 83.6″

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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

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Best season Dec – Feb (peak: Jan)

5Multiple Star System Triple

Components 3 (triple)

Component IDs AC

Separation 83.6″

Companion Mag 11.5

Position Angle 79°

Star Colors A: Orange

Discoverer ES 2628

Separation over time

Measured 1901 → 2021 (120 y)

Separation drift 79.5" → 83.6" (+4.10")

Rate +0.0342" / y

PA drift 81° → 79° (-2°, -0.017°/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.