In this block, the heliacal phases of planets and stars are calculated in a given time range.
Heliacal (ancient Greek ἡλιακός - sunny) — the first sunrise of a celestial body (star or planet) immediately before sunrise after a certain period of invisibility: "sunrise in the rays of the morning dawn".
During the annual movement of the Sun for the terrestrial observer moves among the stars in a direct motion from west to east. Therefore, for some of the stars that set at a given observation latitude, there are time intervals when they are in the daytime sky behind (or next to) the Sun. Over time, the Sun moves relative to the stars to the east, so eventually the star turns out to be west of the Sun and begins to rise in the morning earlier than the Sun. Therefore, at some point in time, when the star rises, it ceases to be lost in the rays of the morning dawn and becomes available for observation. It is believed that on this day there was a heliacal star rising. At different latitudes, the heliacal rising of a star does not necessarily occur on the same day.
Similarly to the heliacal sunrise, there is also a heliacal sunset. There can be 4 phases in total: