Word origin · etymology
Descriptive mapmaking phrase.
Angular refers to chart angles; line names the plotted locus where a body meets a specified angular condition.
How we know · epistemology
Locus of an astronomical condition
Each line joins locations satisfying one specified angular condition at a fixed instant. Rising and setting calculations depend on the adopted horizon model; line proximity is a geometric relationship, not a measured dose of planetary influence.
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Terms used in this explanation
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