When is the best time to observe 20 Monocerotis?

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

Where is 20 Monocerotis located in the sky?

20 Monocerotis lies in the constellation Monoceros at right ascension 07h 10m and declination -04° 14′.

What telescope do I need to split 20 Monocerotis?

Splitting 20 Monocerotis requires an aperture of roughly 60 mm or larger — the components are separated by about 167.9″ at magnitudes near 4.9. The companion is about 5.2 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

20 Monocerotis — Double Star in Monoceros

DoubleStar Monoceros (Mon) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.92

Spectral Type K0III

Star Color Orange (B-V 1.03)

Distance 109 ly

2Position & Identifiers

RA 07h 10m 13.7s

Dec -04° 14' 14.0"

Constellation Monoceros (Mon)

HR 2701

HIP 34622

HD 54810

Flamsteed 20 Mon

SIMBAD

3How easy to split?

Primary 4.9 mag Companion 10.2 mag Separation 167.9″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium+	Medium	Hard+
150 mm Newton 150mm Newt.	Easy	Medium+	Medium+
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 Dec – Feb (peak: Jan)

5Multiple Star System Quadruple

Components 4 (quadruple)

Component IDs AC

Separation 167.9″

Companion Mag 10.2

Position Angle 337°

Star Colors A: Orange

Discoverer ENG 29

Separation over time

Measured 1886 → 2003 (117 y)

Separation drift 190.6" → 167.9" (-22.70")

Rate -0.1940" / y

PA drift 340° → 337° (-3°, -0.026°/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.