A coordinate system designed to give the
s fixed coordinate
s. It is split into
right ascension (ra) and declination
Declination measures from the north celestial
pole to the south celestial pole in
units of degrees, +90 to -90,
modelled on latitude
Ra is measured in hours, the sphere
is split into 24 hours each hour into
minutes and seconds. A star (apart from the sun)
of a given ra will appear in the same place in the sky at the same time of the day. The time of year will dictate
whether or not the sun will also be in the sky
rendering the star invisible.
The principal axis of the celestial sphere is aligned
with the axis of rotation of the earth.
The pole star, Polaris, is so called because it is
the most resaonably bright star closest to this axis on
the sky. There is no southern equivalent.
The zero point of ra is set so that
it corresponds to 0 latitude on the