Alpha Reticuli (α Ret), also catalogued as HIP 19780 and HD 27256, shines at visual magnitude about 3.3. SIMBAD lists it as a late-G giant, with classification G8 IIIa. Some research uses G8 II–III, illustrating that detailed luminosity classifications can differ. Its catalogue parallax is about 20.34 milliarcseconds. Inverting that angle in arcseconds gives an approximate distance of 49 parsecs, or 160 light-years. This distance is an original calculation from the catalogue parallax. Source: SIMBAD, https://simbad.u-strasbg.fr/simbad/sim-basic?Ident=alf+Ret.
Its approved proper name is Rhombus. The IAU adopted that name on 19 September 2024; the announcement published in February 2026 lists it among names approved during 2024 and 2025. The approval applies to the primary component. Alpha Reticuli remains a useful designation because it connects the star to its constellation and to charts that use Greek letters. A proper name does not replace its permanent catalogue identity. Source: IAU, New Star Names 2026, https://www.iau.org/IAU/News/Ann2026/New-Star-Names-2026.aspx.
Rhombus recalls an earlier constellation in this part of the southern sky, associated with Habrecht and later Royer. Lacaille’s eighteenth-century figure became the reticle: historians trace his French name Réticule Rhomboïde and its later Latin form. A rhombus is a quadrilateral with four equal sides; it need not have right angles. The name preserves a geometric and chartmaking history, rather than suggesting that the star itself has that shape. Source: Hoffmann, Azkarrula and Ridpath, https://ase.exopla.net/index.php/Rhombus.
A reticle is a pattern of fine reference lines, such as crosshairs or a grid, in an instrument’s eyepiece. It helps an observer aim or compare positions. Reticulum commemorates that measuring tool, while Reticuli means “of Reticulum.” The constellation name therefore invites a question about measurement: how can astronomers measure a star that appears to us as a point? Source for the official constellation name and genitive: IAU, https://iauarchive.eso.org/public/themes/constellations/.
For this star, one answer came from interferometry. Cusano and colleagues observed HD 27256 with AMBER at the Very Large Telescope Interferometer in December 2008. Combining telescope signals allowed them to measure an apparent diameter of roughly 2.63 milliarcseconds. Their analysis reported a radius near fourteen times the Sun’s, luminosity about ninety-two times the Sun’s, and effective temperature near 4,800 kelvin. These are the study’s results with uncertainties, rather than exact or timeless numbers. Source: Cusano et al., “AMBER/VLTI observations of 5 giant stars,” https://arxiv.org/pdf/1112.5043.
The method links different kinds of evidence. The apparent diameter provides an angular size; a distance lets researchers convert that angle into a physical radius. Light received at Earth helps constrain luminosity and temperature. A revision to the distance can therefore change inferred physical properties without making the angular observation wrong. The interferometer’s ability to measure such a small disk should not be confused with what an ordinary eyepiece resolves. This paragraph explains the measurement relationships in original Star Almanack wording.
Alpha’s reference declination is approximately −62° 28′. Geometrically, it never rises north of about 27.5° N, placing it below the horizon at the almanac’s default 45° N. South of about 27.5° S it is circumpolar: it does not set below a level geometric horizon. At 35° S it reaches about 62.5° altitude at upper culmination. Circumpolar does not mean continuously observable; daylight, weather and obstructions still matter. These limits are original calculations from the catalogue coordinates, ignoring refraction.
Find Alpha within Reticulum’s four-star outline. In the accepted chart, it is the vertex joining the sides toward Epsilon and Beta. Trace both neighbours, then continue around through Delta to confirm the whole figure. Alpha is the brightest of these four stars, but brightness alone is a less reliable identification than the arrangement. Greek-letter labels on the finder and the name Rhombus in the notes refer to the same target. These instructions use the almanac’s preserved finder geometry; the current week supplies changing darkness, Moon conditions and observing times.
