zenith- the point in the sky or celestial sphere directly above an observer
altitude- the apparent height of a celestial object above the horizon, measured as an angle
horizon- a great circle of the celestial sphere, the plane of which passes through the center of the earth and is parallel to that of the apparent horizon of a place.
circompolar stars- (of a star or motion) above the horizon at all times in a given latitude.
astrolabe- One of the fundamental calculations in astrology is the position of the sun relative to the signs of the zodiac. The path of the sun as seen from Earth is called the ecliptic and the astrolabe calculates the position of the sun on this path.
doppler effect- The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It is named after the Austrian physicist Christian Doppler, who described the phenomenon in 1842.
