SOME BASICSASTRONOMY - Study of celestial/astronomic/universalobjects/bodies and the phenomenon surrounding them.CELESTIAL OBJECTSStarsPlanetsCometsAsteroidsVIRGO>LOCAL GROUP>MILKY WAY>SOLARSYSTEM>EARTHASTRONOMICAL SURVEY / FIELD ASTRONOMY helps indetermination of latitude & longitudedetermination of distances for satellite communicationdetermination of route for space ships & shuttles
CELESTIAL SPHEREFIXED STARThey are celestial objects that do not seem to movein relation to the other stars of the night skyCELESTIAL SPHERETo make it easier to understand the motions ofobjects in our skies, astronomers often depict thespace as a sphere concentric to the earth,surrounding the Earth with the earth as centre and afixed star as a point in the circumference of sphere.CELESTIAL SPHERE - DEFINITIONIt is defined as an imaginary sphere upon thesurface of which all stars in the sky appear to bestudded to an observer stationed at its centre.CELESTIAL BODY & OBSERVER
MOVEMENT OF SUNAlthough the stars are fixed relative to each other, the Sun movesrelative to the stars.Once a year, the Sun traces out a circle on the celestial spherecalled the ecliptic, which is tilted at an obliquity of 23.5° withrespect to the celestial equator.The Sun crosses the celestial equator at exactly two points, calledequinoxes, from the Latin for "equal nights“The equinox where the Sun ascends from the southern to thenorthern hemisphere is called the spring or vernal equinoxbecause the Sun is there on March 21. The vernal equinox ischosen to be 0 h R.A.The Sun again crosses the celestial equator halfway around, at 12 hR.A. This position is called the autumnal equinox because the Sunis there on September 23.
MOVEMENT OF SUNThe positions where the Sun reaches its highest and lowest pointsare called solstices, from the Latin for "the Sun stops" as itchanges direction.The Sun is highest in the sky (in the northern hemisphere) when it isat 6 h R.A. This position is called the summer solstice because theSun is there on June 21. The Sun then has a declination of +23.5°.The Sun is lowest in the sky (in the northern hemisphere) when it isat 18 h R.A. This position is called the winter solstice because theSun is there on December 21. The Sun then has a declination of-23.5°.
CO – ORDINATE SYSTEMS1. ALTITUDE & AZIMUTH SYSTEM (HORIZONTAL SYSTEM)2. DECLINATION RIGHT ASCENSION SYSTEM (INDEPENDENTEQUATORIAL SYSTEM)3. DECLINATION HOUR ANGLE SYSTEM (DEPENDENTEQUATORIAL SYSTEM)