Download Declination - School

Declination
demonstrate an understanding of the terms ‘right ascension’ and ‘declination’
Latitude and longitude are the way we define a point on the Earth's surface. There is a similar system for defining a
point on the celestial sphere and that is using declination and right ascension.
The declination of a star is its angle above the celestial equator.
Just as the North Pole has a latitude of 90 degrees then Polaris has a declination of 90 degrees. Any point on the
Earth's equator has a declination of zero and so any point on the celestial equator has a declination of zero.
As the Earth rotates inside the celestial equator the stars appear to rotate anticlockwise around Polaris, rising in the
East and setting in the West. Their position in the sky may change but they are fixed on the celestial sphere. Their
declination does not change.
If we know the declination of a star then we can work out how far away from Polaris it is. A star with a declination of 80
degrees would be just 10 degrees from Polaris. A star with a declination of 60 degrees would be 30 degrees from
Polaris. etc.
In the animation above we are looking North from a place which has a latitude of 55 degrees. The point z is called our
zenith. It is directly above our head.