When is the best time to observe Alpha Circini?

Alpha Circini is best observed from March through May, with peak visibility during April when it transits around midnight in the Northern Hemisphere.

Where is Alpha Circini located in the sky?

Alpha Circini lies in the constellation Circinus at right ascension 14h 43m and declination -64° 59′.

What telescope do I need to split Alpha Circini?

Splitting Alpha Circini requires an aperture of roughly 60 mm or larger — the components are separated by about 15.7″ at magnitudes near 3.2. The companion is about 5.3 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Alpha Circini — Double Star in Circinus

Magnitude 3.2^m DoubleStar Circinus (Cir) Visible

Star Map + List + Plan

About Alpha Cir

Description

Alpha Circini is a chemically peculiar star of spectral type ApSrEuCr at magnitude 3.19, the brightest star in Circinus (the Compass). Located about 54 light-years from Earth, it is the nearest rapidly oscillating Ap (roAp) star — a class of stars that pulsate in high-overtone non-radial modes with periods of only a few minutes.

Observing Tips

Alpha Cir lies in the small constellation Circinus, just west of Alpha Centauri. It is easily found due to its proximity to the brilliant Alpha Cen. Only visible from the southern hemisphere. Best observed April through July.

History

Circinus was created by Nicolas Louis de Lacaille in the 1750s and represents a pair of dividing compasses. Alpha Circini has no traditional proper name. Its discovery as a rapidly oscillating Ap star in 1981 opened a new field of stellar pulsation studies.

Fun Facts

Alpha Cir oscillates with a period of only 6.8 minutes — one of the shortest pulsation periods known for any star. These rapid pulsations are thought to be aligned with the magnetic axis rather than the rotation axis, creating a unique 'oblique pulsator' model.

Observe

1Physical Properties

Magnitude 3.19

Range 3.17 - 3.19

Period 0.1 hours

Variable Type roAp+ACV

Spectral Type A7VpSrCrEu Kn

Star Color Yellow-white (B-V 0.24)

Distance 54 ly

2Position & Identifiers

RA 14h 42m 30.4s

Dec -64° 58' 31.0"

Constellation Circinus (Cir)

HR 5463

HIP 71908

HD 128898

SAO 252853

Bayer Alpha

Variable ID Alp Cir

SIMBAD

3How easy to split?

Primary 3.2 mag Companion 8.5 mag Separation 15.7″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Medium+	Medium+	Medium+
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

Set a location in User Settings to see visibility data.

Best season Mar – May (peak: Apr)

5Light Curve

6Multiple Star System C: optical

Separation 15.7″

Companion Mag 8.5

Position Angle 224°

Star Colors A: Yellow-white

Discoverer DUN 166

Notes

Binary. Companion K5V.

Separation over time

Measured 1826 → 2016 (190 y)

Separation drift 10.0" → 15.7" (+5.70")

Rate +0.0300" / y

PA drift 263° → 224° (-39°, -0.205°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

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.