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heliacal (huh-LEYE-uh-kuhl) - adj., especially of a star, the first time it is visible at sunrise (after being in conjunction) or the last time it is visible at sunset (before going into conjunction).
This is an ancient concept, as you might expect given the "visibility" standard is for with the naked eye. There were also helical years used for ex in ancient Egypt, which started with the helical rise of Sirius (also sometimes canicular year), and by the Maoris, which started with the helical rise of the Pleiades. Note that circumpolar stars never have helical days, as they are always visible at night. The word was borrowed in 1607 from Latin hēliacus, from Greek hēliakós, of or pertaining to the sun.
---L.
This is an ancient concept, as you might expect given the "visibility" standard is for with the naked eye. There were also helical years used for ex in ancient Egypt, which started with the helical rise of Sirius (also sometimes canicular year), and by the Maoris, which started with the helical rise of the Pleiades. Note that circumpolar stars never have helical days, as they are always visible at night. The word was borrowed in 1607 from Latin hēliacus, from Greek hēliakós, of or pertaining to the sun.
---L.
