When is the best time to observe HIP 42540?

HIP 42540 is best observed from December through February, with peak visibility during January when it transits around midnight in the Northern Hemisphere.

Where is HIP 42540 located in the sky?

HIP 42540 lies in the constellation Vela at right ascension 08h 40m and declination -40° 16′.

What telescope do I need to split HIP 42540?

Splitting HIP 42540 requires an aperture of roughly 100 mm or larger — the components are separated by about 4.6″ at magnitudes near 5.2. The companion is about 3.9 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

HIP 42540 — Double Star in Vela

Magnitude 5.2^m DoubleStar Vela (Vel) Visible

Star Map + List + Plan Star Hop

Observe

1Physical Properties

Magnitude 5.20

Spectral Type B9V

Star Color Blue-white (B-V -0.01)

2Position & Identifiers

RA 08h 40m 19.3s

Dec -40° 15' 51.0"

Constellation Vela (Vel)

HR 3439

HIP 42540

HD 74067

SAO 220252

SIMBAD

3How easy to split?

Primary 5.2 mag Companion 9.1 mag Separation 4.6″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard+	Hard+	Hard+
150 mm Newton 150mm Newt.	Medium+	Medium+	Medium+
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

Set a location in User Settings to see visibility data.

Best season Dec – Feb (peak: Jan)

5Multiple Star System

Separation 4.6″

Companion Mag 9.1

Position Angle 68°

Star Colors A: Blue-white B: Yellow

Discoverer COO 74

Notes

Companion A2V.

Separation over time

Measured 1894 → 2016 (122 y)

Separation drift 3.8" → 4.6" (+0.80")

Rate +0.0066" / y

PA drift 61° → 68° (+7°, +0.057°/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.