Measuring declination allows one to find the angle of celestial objects like the sun above or below the celestial equator. Declination is part of the equatorial coordinate system used to map objects' positions. Simple equations can be used to calculate an object's declination based on the day of the year, for example the sun's declination on October 30th is approximately -19.11 degrees. Declination is primarily used for celestial mapping but can also determine the angle of sunlight for a location on Earth.

1. Declination-Angle of the SunFinding the angle of an object above or below the equator

2. DeclinationDeclination is the latitudinal part of the equatorial coordinate system, which is used to map celestial objects.Declination can be used to find the angle of a celestial object above or below the equator, such as the sun.

3. Key TermsIn the equatorial coordinate system, there are several key terms used.The ecliptic is similar to the equator , but is not tilted at an angle.Right Ascension is used to measure longitudinal angles.Often these are called “celestial,” such as the celestial equator.

4. Practical UsesMeasuring declination is primarily used for mapping celestial objects.It can be used for the sun to find the angle of sunlight for a position on earth.

5. Finding DeclinationThere are relatively simple equations which can be used to find declination.The equation can be used, where d = the day of the year.With this equation, the day October 30, which is the 303rd day of the year, has an approximate declination angle of -19.11˚.

6. Sources"Declination -." Wikipedia, the free encyclopedia. Web. 02 Nov. 2009. http://en.wikipedia.org/wiki/Declination."Declination Angle of the Sun." PVCDROM. Web. 02 Nov. 2009. http://pvcdrom.pveducation.org/SUNLIGHT/DECLIN.HTM."Equatorial Coordinate." Web. http://hyperphysics.phy-astr.gsu.edu/hbase/solar/imgsol/eclip3.gif.