Celestial Sphere Flashcards
why have the Celestial Sphere?
used to facilitate thinking about Celestial Navigation
what is the Sidereal Day when using the Celestial Sphere?
- is period of rotation of Earth relative to stars
- is time between successive transits of the First Point of Aries above the meridian
how many of the celestial objects are on the Celestial Sphere?
all
what do Solar system objects orbit around?
Sun
Solar system bodies move on the Celestial Sphere relative to what?
the background of stars
what is the Celestial Sphere?
an imaginary sphere of infinite radius concentric with the Earth
what are Celestial Poles?
extensions of Earth’s axis of rotation
where is Earth in the Celestial Sphere?
stationary at the centre
how often + what direction does the Celestial Sphere rotate?
westwards once per sidereal day
what is the Equinoctial equivalent to + why?
Equator - is perpendicular to Earth’s axis
what is the Ecliptic?
the path of the Sun through the year
what is the 1st point of Aries?
- the point of intersection of the Ecliptic + the Equinoctial
- Sun moving Northwards
- Vernal Equinox
what is the 1st point of Libra?
- point of intersection of the ecliptic + the Equinoctial
- Sun moving Southwards
- Autumnal Equinox
what are the approximate dates of The Southern Solstice?
- 21st March
- June
- September
- December
why is the movement of the 1st point of Aries constant?
it depends purely on the rotation of the Earth on its axis
