Star Card

Projection Method: The celestial map plate is a projection of the celestial sphere, created using the principle of polar equidistant projection. One plate centers on the North Celestial Pole, while the other centers on the South Celestial Pole.

Content: Features aviation stars (first-magnitude, second-magnitude, and select third-magnitude stars), the celestial equator, the ecliptic, and the local hour angle (or celestial right ascension) of the vernal equinox, along with the date of the mean solar time.

Each set comprises 13 sheets, each depicting a series of contour lines for elevation and azimuth at intervals of 0°, 5°, 10°, ... 60° latitude. Each transparent horizontal coordinate grid is dual-purpose for both northern and southern hemisphere surveyors, marked with N and S respectively.

Content:

① The central “+” indicates the observer's zenith, with radial curves representing celestial azimuth circles marked with directional readings at their ends. Inner numbers denote the celestial azimuth as seen by observers in northern latitudes; outer numbers indicate the celestial azimuth as seen by observers in southern latitudes.

② The horizontal closed circular curve represents the celestial altitude parallel circle;

③ The chart features rectangular notches for marking planetary positions, with latitude scales within ±30° north and south on both sides. On the transparent horizontal coordinate grid, two parallel lines indicating solar altitudes of -6° and -12° are marked on either side.

2. Using a star chart to select and identify stars

Using a star chart to select and identify stars typically involves three steps:

   (1) Plot the observable planetary positions on the star chart baseplate;

   ⑵Determine the observable starry sky based on the observer's latitude;

   ⑶ Star selection and identification based on the observable night sky.