When is the best time to observe HIP 42172?

HIP 42172 is best observed from December through February, with peak visibility during January when it transits around midnight in the Northern Hemisphere.

Where is HIP 42172 located in the sky?

HIP 42172 lies in the constellation Cancer at right ascension 08h 36m and declination +06° 37′.

What telescope do I need to split HIP 42172?

Splitting HIP 42172 requires an aperture of roughly 60 mm or larger — the components are separated by about 10.1″ at magnitudes near 6.0. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 42172 — Double Star in Cancer

Observable Double Star Excellent (66/100)

Sep: 10.1", Companion: mag 7.2

Magnitude 6.0^m DoubleStar Cancer (Cnc) Visible

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Observe

1Physical Properties

Magnitude 5.99

Spectral Type F8V

Star Color Yellow (B-V 0.52)

Distance 63 ly

2Position & Identifiers

RA 08h 35m 51.0s

Dec +06° 37' 12.0"

Constellation Cancer (Cnc)

HR 3395

HIP 42172

HD 72945

SAO 116929

Double Cat 6886

SIMBAD

3How easy to split?

Primary 6.0 mag Companion 7.2 mag Separation 10.1″

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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 Dec – Feb (peak: Jan)

5Multiple Star System Quintuple C,D,E,F: optical

Components 5 (quintuple)

Component IDs AB

Separation 10.1″

Companion Mag 7.2

Companion Sp G5V

Position Angle 25°

Star Colors A: Yellow B: Orange

Discoverer STF1245

Notes

CPM with HR 3396.

Separation over time

Measured 1782 → 2022 (240 y)

Separation drift 12.5" → 10.1" (-2.40")

Rate -0.0100" / y

PA drift 27° → 25° (-2°, -0.008°/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.