When is the best time to observe HIP 20904?

HIP 20904 is best observed from October through December, with peak visibility during November when it transits around midnight in the Northern Hemisphere.

Where is HIP 20904 located in the sky?

HIP 20904 lies in the constellation Taurus at right ascension 04h 29m and declination +30° 22′.

What telescope do I need to split HIP 20904?

Splitting HIP 20904 requires an aperture of roughly 60 mm or larger — the components are separated by about 14.9″ at magnitudes near 6.4. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 20904 — Double Star in Taurus

Magnitude 6.4^m DoubleStar Taurus (Tau) Visible

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Observe

1Physical Properties

Magnitude 6.40

Spectral Type F7V

Star Color Yellow (B-V 0.52)

Distance 204 ly

2Position & Identifiers

RA 04h 28m 51.9s

Dec +30° 21' 41.0"

Constellation Taurus (Tau)

HR 1406

HIP 20904

HD 28271

SAO 57249

Double Cat 3243

SIMBAD

3How easy to split?

Primary 6.4 mag Companion 8.0 mag Separation 14.9″

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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 Quadruple C: optical

Components 4 (quadruple)

Component IDs AB

Separation 14.9″

Companion Mag 8.0

Position Angle 36°

Star Colors A: Yellow B: Orange

Discoverer STF 548

Notes

AB binary; C, 11.32V at 121" optical. Fourth component 13.3v at 17" from C.

Separation over time

Measured 1823 → 2020 (197 y)

Separation drift 15.3" → 14.9" (-0.40")

Rate -0.0020" / y

PA drift 34° → 36° (+2°, +0.010°/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.