What does the theoretical moonrise time on an astronomical calendar actually represent?
Answer
The moment the moon reaches zero degrees of altitude above the horizon
Most astronomical resources and calendars calculate moonrise based on a theoretical, perfectly flat horizon, defined as zero degrees of altitude. This represents the geometric moment the top edge of the moon clears the horizontal plane from the center of a city. However, this calculation is mathematical and does not take into account the reality of the local environment, such as the elevation of the observer or the existence of nearby buildings or mountains that might delay the view.
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