When is the best time to observe 15 Hydrae?

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

Where is 15 Hydrae located in the sky?

15 Hydrae lies in the constellation Hydra at right ascension 08h 52m and declination -07° 11′.

What telescope do I need to split 15 Hydrae?

Splitting 15 Hydrae requires an aperture of roughly 150 mm or larger — the components are separated by about 1.2″ at magnitudes near 5.5. Larger apertures and steady seeing help resolve the pair cleanly.

15 Hydrae — Double Star in Hydra

Observable Double Star Fair (27/100)

Sep: 1.2", Companion: mag 7.4

Magnitude 5.5^m DoubleStar Hydra (Hya) Visible

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Observe

1Physical Properties

Magnitude 5.54

Spectral Type A4m

Star Color White (B-V 0.15)

Distance 297 ly

2Position & Identifiers

RA 08h 51m 34.5s

Dec -07° 10' 38.0"

Constellation Hydra (Hya)

HR 3523

HIP 43496

HD 75737

SAO 136345

Flamsteed 15 Hya

Double Cat 7050

SIMBAD

3How easy to split?

Primary 5.5 mag Companion 7.4 mag Separation 1.2″

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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	Medium

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 Quadruple

Components 4 (quadruple)

Component IDs AB

Separation 1.2″

Companion Mag 7.4

Position Angle 118°

Star Colors A: White B: Yellow

Discoverer BU 587

Notes

AB binary. Other components optical.

Separation over time

Measured 1878 → 2021 (143 y)

Separation drift 0.50" → 1.2" (+0.70")

Rate +0.0049" / y

PA drift 160° → 118° (-42°, -0.294°/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.