Equatorial Armilla

Qing Dynasty, 1673
Ancient Observatory, Beijing

This armilla takes a set of readings that complements the ecliptic armilla seen on the previous pages; according to the signage, it measures "the true solar time¹ as well as the right ascension difference² and declination³ of celestial bodies." Its supporting pillars are incrusted with a riot of exuberant decoration.

¹True solar time = apparent solar time = local solar time. It is the angle of the sun above the horizon as seen by an observer or measured by a sundial.

²Right ascension (RA) = celestial longitude; RA difference = the difference in right ascension between the sun and a celestial body.

³Declination = celestial latitude. See: Astronomy For Beginners.