Cursa is Beta Eridani (β Eri), permanent object 752, and is also HD 33111 and HIP 23875. SIMBAD records a visual magnitude near 2.79, spectral type A3 IV, parallax 36.2456 ± 0.3575 milliarcseconds and substantial proper motion: https://simbad.cds.unistra.fr/simbad/sim-id?Ident=Beta+Eridani. A simple inversion of that parallax gives about 27.6 parsecs, or 90 light-years. The small fractional uncertainty makes that a useful scale estimate, though this account does not substitute its own distance fit for the catalogue measurement.
An A3 spectrum explains the blue-white point seen by the eye, while luminosity class IV indicates a subgiant—an object beginning to evolve away from the main sequence. Older references sometimes give a neighbouring luminosity class, a reminder that spectral classification draws boundaries across continuous stellar properties. The securely observed facts are the spectrum, brightness, astrometric motion and parallax; a concise class label is the astronomer's interpretation of them.
SIMBAD's proper-motion components also show that Cursa shifts by a little over a tenth of an arcsecond per year against much more distant background objects. That is imperceptible over one observing season, but measurable across long astrometric baselines and consistent with a relatively nearby star rather than the distant Orion association.
The IAU-approved proper name Cursa comes from an Arabic expression traditionally understood as the footstool or chair of Orion. That makes sense on the sky: the star sits just northwest of Rigel, while Eridanus begins nearby and winds away as the celestial River. The IAU's Working Group on Star Names standardizes Cursa for Beta Eridani: https://www.iau.org/public/themes/naming_stars/. Eridanus itself is an official constellation, abbreviation Eri and genitive Eridani: https://www.iau.org/IAU/IAU/Astronomy-FAQs/Constellations.aspx.
The stored position is approximately right ascension 5h 07m 51s and declination −5° 05′. At latitude 45° N it reaches about 40° altitude at upper culmination; at 35° S it reaches about 60°. These are original coordinate calculations that ignore refraction, obstructions and daylight. Its declination makes Cursa available from most inhabited latitudes, unlike the far-southern Beta Mensae.
For naked-eye identification, find brilliant Rigel at Orion's southwest corner and look a short step to the northwest for the distinctly fainter Cursa. Confirm the point against the opening bend of Eridanus rather than choosing any nearby Orion star. Binoculars make the relationship easy under city glow. From Cursa, the stored coordinates place NGC 1788 about 1.77° almost due north—close enough for many low-power telescope fields or a short controlled sweep. That separation is an original spherical calculation. The accepted rendered finder and reader link have not yet been checked, so the route still needs publication-stage verification.
Cursa needs no telescope, and high power will not reveal a surface disk. The most instructive use of the star is as an anchor: a bright nearby A-type subgiant in the foreground of our line of sight, and a signpost to a dusty star-forming cloud much farther away. Apparent proximity on the sky is not physical companionship.
An observation can compare Cursa's blue-white impression with Rigel while allowing for the Purkinje effect, atmospheric extinction and the eye's poor colour response at low light. Do not turn a subtle hue into a temperature measurement. Save Moon phase, twilight and the week's timing for the changing calendar conditions; the reusable story is the nearby subgiant marking the River's beginning.
