The chart is dedicated to King Charles II and the constellations include Robur Carolinum (King Charles' oak tree). The chart contains a key for six magnitudes of stars. There are diagrams in the four corners of the sheet: that at the top left shows the sun and the ingress of Mercury observed by Halley at St Helena on October 28 1677; that at top right shows the sun and the exit of Mercury; at bottom left is a diagram to explain the use of spherical triangles in calculating right ascension and declination, and at bottom right, the use of spherical triangles to calculate the position and distance of unknown stars.