When is the best time to observe 10 Monocerotis?

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

Where is 10 Monocerotis located in the sky?

10 Monocerotis lies in the constellation Monoceros at right ascension 06h 28m and declination -04° 46′.

What telescope do I need to split 10 Monocerotis?

Splitting 10 Monocerotis requires an aperture of roughly 60 mm or larger — the components are separated by about 77.0″ at magnitudes near 5.1. The companion is about 4.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

10 Monocerotis — Double Star in Monoceros

Magnitude 5.1^m DoubleStar Monoceros (Mon) Visible

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Observe

1Physical Properties

Magnitude 5.06

Spectral Type B2V

Star Color Blue (B-V -0.17)

2Position & Identifiers

RA 06h 27m 57.6s

Dec -04° 45' 44.0"

Constellation Monoceros (Mon)

HR 2344

HIP 30772

HD 45546

SAO 133290

Flamsteed 10 Mon

SIMBAD

3How easy to split?

Primary 5.1 mag Companion 9.6 mag Separation 77.0″

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

5Multiple Star System Triple

Components 3 (triple)

Component IDs AB

Separation 77.0″

Companion Mag 9.6

Position Angle 257°

Star Colors A: Blue B: Yellow

Discoverer BUP 89

Separation over time

Measured 1879 → 2002 (123 y)

Separation drift 77.0" → 77.0" (+0.00")

Rate +0.0000" / y

PA drift 257° → 257° (+0°, +0.000°/y)

Essentially fixed on human timescales — the same view your grandchildren will see.

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.