ASTR 114 1st EditionThe Story Night, Seasons and TimeLecture 2Questions for thoughtWhat does the universe look like? Why do stars rise and set?Why do the constellations we see depend on latitude and time of year?Constellation - A region of the sky, there are 88 in existenceThe Celestial SphereStars at different distances all appear to lie on the celestial sphere The 88 official constellations cover the sphere Ecliptic - The sun apparent path through the celestial sphereThe Local Sky - An objects altitude (above the horizon) and azimuth (direction along thehorizon) specify its location in your local sky.Zenith - The point directly overheadHorizon - All points 90 degrees away from zenithDaily Motions (of stars and the sun)Earth rotates from west to east, so stars appear to circle from east to west. Seasons are caused by the earth revolving around the sun. Lengths of days, and monthsA solar day is longer than a sidereal day by about 1/360 because earth moves about 1 degree in orbit each day. !1Thursday, January 29, 2015• The length of a day according to our clocks is from solar noon to solar noon. *You must know the difference between sidereal and synodic *Sidereal: 360 degrees of revolutionSynodic: The time it takes to return to the same geometrySidereal Month - Moon orbits earth in 27.3 days. Earth and moon travel 30 degrees around the sun during that time.Synodic Month - A cycle of lunar phases. It’s 1/12 longer than a sidereal month. Sidereal Year - Time for earth to go once around the