When is the best time to observe BN Hydri?

BN Hydri is best observed from October through December, with peak visibility during November when it transits around midnight in the Northern Hemisphere.

Where is BN Hydri located in the sky?

BN Hydri lies in the constellation Hydrus at right ascension 03h 08m and declination -78° 59′.

What telescope do I need to split BN Hydri?

Splitting BN Hydri requires an aperture of roughly 60 mm or larger — the components are separated by about 15.2″ at magnitudes near 5.6. Larger apertures and steady seeing help resolve the pair cleanly.

BN Hydri — Double Star in Hydrus

Observable Double Star Excellent (60/100)

Sep: 15.2", Companion: mag 7.7

DoubleStar Hydrus (Hyi) Visible

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Observe

1Physical Properties

Magnitude 5.57

Spectral Type F2II-III

Star Color Yellow-white (B-V 0.30)

2Position & Identifiers

RA 03h 07m 32.0s

Dec -78° 59' 22.0"

Constellation Hydrus (Hyi)

HR 981

HIP 14521

HD 20313

Variable ID BN Hyi

SIMBAD

3How easy to split?

Primary 5.6 mag Companion 7.7 mag Separation 15.2″

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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

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Best season Oct – Dec (peak: Nov)

5Multiple Star System

Separation 15.2″

Companion Mag 7.7

Position Angle 225°

Star Colors A: Yellow-white B: Yellow

Discoverer HJ 3568

Notes

Secondary 8.06V.

Separation over time

Measured 1836 → 2015 (179 y)

Separation drift 14.5" → 15.2" (+0.70")

Rate +0.0039" / y

PA drift 222° → 225° (+3°, +0.017°/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.