When is the best time to observe HIP 81657?

HIP 81657 is best observed from April through June, with peak visibility during May when it transits around midnight in the Northern Hemisphere.

Where is HIP 81657 located in the sky?

HIP 81657 lies in the constellation Ara at right ascension 16h 41m and declination -60° 27′.

What telescope do I need to split HIP 81657?

Splitting HIP 81657 requires an aperture of roughly 250 mm or larger — the components are separated by about 1.3″ at magnitudes near 6.2. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 81657 — Double Star in Ara

Magnitude 6.2^m DoubleStar Ara Visible

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Observe

1Physical Properties

Magnitude 6.18

Spectral Type F2III-IV giant

Star Color Yellow (B-V 0.48)

2Position & Identifiers

RA 16h 40m 50.5s

Dec -60° 26' 46.0"

Constellation Ara

HR 6177

HIP 81657

HD 149837

SAO 253651

SIMBAD

3How easy to split?

Primary 6.2 mag Companion 9.1 mag Separation 1.3″

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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.	Hard	Hard	Hard
Celestron C8 (203 mm SCT) C8 203mm	Hard+	Hard+	Hard+

Easy Medium Hard Very hard Impossible

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

To reach "Medium" at Bortle 3, you'd need at least a 250 mm reflector.

4Visibility

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Best season Apr – Jun (peak: May)

5Multiple Star System

Separation 1.3″

Companion Mag 9.1

Position Angle 35°

Star Colors A: Yellow B: Orange

Discoverer B 1818

Separation over time

Measured 1930 → 2016 (86 y)

Separation drift 1.2" → 1.3" (+0.10")

Rate +0.0012" / y

PA drift 33° → 35° (+2°, +0.023°/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.