When is the best time to observe Mu Octantis?

Mu Octantis is best observed from June through August, with peak visibility during July when it transits around midnight in the Northern Hemisphere.

Where is Mu Octantis located in the sky?

Mu Octantis lies in the constellation Octans at right ascension 20h 42m and declination -75° 21′.

What telescope do I need to split Mu Octantis?

Splitting Mu Octantis requires an aperture of roughly 60 mm or larger — the components are separated by about 16.7″ at magnitudes near 6.5. Larger apertures and steady seeing help resolve the pair cleanly.

Mu Octantis — Double Star in Octans

Mu Oct (BS7864)

Magnitude 6.5^m DoubleStar Octans (Oct) Visible 2 Exoplanets

Star Map + List + Plan Star Hop

Observe

1Physical Properties

Magnitude 6.55

Spectral Type G5III giant

Star Color Yellow (B-V 0.62)

2Position & Identifiers

RA 20h 41m 43.7s

Dec -75° 21' 02.0"

Constellation Octans (Oct)

HR 7864

HIP 102125

HD 196067

SAO 257836

Bayer Mu

SIMBAD Wikipedia

3How easy to split?

Primary 6.6 mag Companion 7.1 mag Separation 16.7″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
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

Set a location in User Settings to see visibility data.

Best season Jun – Aug (peak: Jul)

5Multiple Star System

Separation 16.7″

Companion Mag 7.1

Position Angle 20°

Star Colors A: Yellow B: Yellow

Discoverer DUN 232

Notes

CPM. Companion G5V.

Separation over time

Measured 1826 → 2023 (197 y)

Separation drift 18.5" → 16.7" (-1.80")

Rate -0.0091" / y

PA drift 14° → 20° (+6°, +0.030°/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.