Meridian Passage and Polaris

The ‘meridian passage’ of a heavenly bodyHeavenly body occurs when it is in the observer’s meridian or in the meridian 180° from the observer’s meridian. At that moment, the local hour angle of the heavenly body will be either 0° or 180°, and the heavenly body is either due North or due SouthSouth (i.e., bearing 180° or 000°) from the observer. The position line obtained, being at right-angles to the bearing, will instantly give the observer’s latitude. Although sights can be taken for the meridian passage of any heavenly body, it is normally only observed for the SunSun. Occasionally, Jupiter and VenusVenus may also be usefully observed by day.