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Lecture 5

AS101 Lecture Notes - Lecture 5: Celestial Equator, Declination, Northern Hemisphere


Department
Astronomy
Course Code
AS101
Professor
Patrick Mc Graw
Lecture
5

Page:
of 2
Astronomy- Lecture 5
Declination
- Analog to the latitude to the map
- Altitude means roughly how far something is
- Stars altitude varies as the earth rotates
- The altitude of the stars keep on changing through the course of the night
- Declination is the angular distance from the celestial equator.
- The declination is how far or south we are from the equator belt
- Declination for a start is fixed, altitude is not
Latitude affects what you can see
- If we are sitting at the north pole then NCP is directly at the zenith
- The altitude of the NCP is equal to the observer
Historical importance of seasonal cycle
- Summer solstice is the first day of the summer
Consider the orbit fo the Earth
- The earth`s orbit is a circle
Mystery
- This is because the earth is on a tilt
- They are opposites
What is the Trend?
- The beam area got larger
- It went into a different shape
- It was concentrated on a small area
- The amount of light in each of those 3 circles got smaller and smaller
Annual motion of the Earth
- The earth revolves once around the sun in 365 days and remains tilted at 23.5 degrees
- Ecliptic is the plane of the earth`s orbit around the sun
Northern Summer Solstice: 6/21
- We get more concentrated energy at the start of summer
Northern Winter Solstice: 12/21
- Northern Hemisphere sunlight hits the surface at a grazing angle
- Energy spreads out
- Start of Winter
- Southern Hemisphere, Sunlight hits the surface a ta nearly perpendicular angle
- More concentrated energy
- Start of summer