When is the best time to observe Rho Hydrae?

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

Where is Rho Hydrae located in the sky?

Rho Hydrae lies in the constellation Hydra at right ascension 08h 48m and declination +05° 50′.

What telescope do I need to split Rho Hydrae?

Splitting Rho Hydrae requires an aperture of roughly 60 mm or larger — the components are separated by about 12.2″ at magnitudes near 4.4. The companion is about 7.5 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Rho Hydrae — Double Star in Hydra

Magnitude 4.4^m DoubleStar Hydra (Hya) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.36

Spectral Type A0Vn

Star Color Blue-white (B-V -0.04)

Distance 233 ly

2Position & Identifiers

RA 08h 48m 26.0s

Dec +05° 50' 16.0"

Constellation Hydra (Hya)

HR 3492

HIP 43234

HD 75137

SAO 117146

Bayer Rho

Flamsteed 13 Hya

Double Cat 7006

SIMBAD

3How easy to split?

Primary 4.4 mag Companion 11.9 mag Separation 12.2″

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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	Medium	Medium	Hard+

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

Separation 12.2″

Companion Mag 11.9

Position Angle 147°

Star Colors A: Blue-white

Discoverer AGC 3

Notes

CPM.

Separation over time

Measured 1878 → 2022 (144 y)

Separation drift 12.4" → 12.2" (-0.20")

Rate -0.0014" / y

PA drift 145° → 147° (+2°, +0.014°/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.