Positional astronomyPositional astronomy
is the study of the positions of celestial objects. This is the oldest branch of astronomy
and dates back to antiquity
. Observations of celestial objects are important for religious and astrological
purposes, as well as for timekeeping.
Ancient structures associated with positional astronomy include:
The unaided human eye can detect about 6000 stars
, of which about half are below the horizon at any one time.
On modern star charts, the celestial sphere is divided into 88 constellations. Every star lies within a constellation.
Constellations are useful for navigation. If you live in the northern hemisphere you can find north by locating the star Polaris. This star is always at a position nearly over the north pole.
, diurnal motion
, Halley, Edmund
, History of Astronomy
, Kepler's laws of planetary motion
, prograde and retrograde motion
, sidereal time
, Chinese astrology