Brief introduction of daily trail

In astronomy, the daily track (pronounced/? n？ l？ m？ /,which means the base of the sundial in Greek, is a curve on the celestial sphere, which is used to indicate the angular deviation between the average position of another celestial body (usually the sun) observed by an observer on one celestial body and the actual position. For example, we know that the lunar day of the Earth is close to 24 hours. If we calibrate the position of the sun on the celestial sphere at the same time every day throughout the year, we can draw the daily trajectory. Finally, draw the daily trajectory curve into the shape of Arabic numeral 8. This curve can usually be drawn on a globe, and it is usually most likely to be drawn in the East Pacific Ocean, which is the only tropical area with almost no land. Although shooting the trajectory of the next day is quite challenging, it is still possible to shoot successfully by keeping the camera in a fixed position for a whole year and shooting at intervals of 24 hours (or multiples thereof). The northern and southern parts of the sun's trajectory are its declination, that is, the latitude of direct sunlight. The east-west part is the average time difference, that is, the difference between the solar day and the local average time. This can explain why the speed of the sun is sometimes "fast" and sometimes "slow" compared with the clock time. There are three factors that will affect the size and shape of the sun's trajectory: the axial inclination, the eccentricity of the orbit and the intersection angle between the point-to-point line and the point-to-point line of the semi-circular arch. For a celestial body with a perfect circular orbit and an axis without inclination, the sun is always in the same place at the same time every day of the year, so the daily orbit will be a point. However, for a celestial body with a circular orbit but an inclined axis, its daily trajectory is in the shape of Arabic numeral 8, and the circles in the northern half and the southern half are equal in size. A celestial body whose orbit is elliptical but its axis is not inclined is a straight line along the equator. The daily trajectory containing images of total solar eclipse is called Tutulemma, which is a term coined by astronomical photographers and comes from the Turkish solar eclipse.