1 / 22

Announcements

Announcements. Homework Set 1 is due today Homework set 2: Chapter 2 # 32, 35, 37, 39, 43, 44, 45 & 49 Use Exam Formula Sheet as you do the homework to familiarize yourself with where things are on it. Hint for #44 & 45. Terrestrial Coordinates.

titus
Download Presentation

Announcements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Announcements • Homework Set 1 is due today • Homework set 2: Chapter 2 # 32, 35, 37, 39, 43, 44, 45 & 49 • Use Exam Formula Sheet as you do the homework to familiarize yourself with where things are on it.

  2. Hint for #44 & 45

  3. Terrestrial Coordinates Longitude is measured CCW (+) or CW (-) around from Greenwich England Latitude is measured North or South of the equator Both are measured in degrees, minutes and seconds Show hint for problem #37

  4. Celestial Coordinates The angle between the celestial equator and the ecliptic is 23.5° Right Ascension (RA) is measured CCW from the Vernal Equinox and is in hours, minutes and seconds Declination (Dec) is measured above (+) or below (-) the celestial equator and is in degrees, minutes and seconds See Appendix A6 for more on celestial coordinates

  5. Finding the CE and NCP at your latitude Altitude of NCP above due north horizon along the meridian is just f, your latitude (+ for north, - for south) Altitude of the celestial equator above due south horizon along the meridian is 90°-f

  6. Example Chapter 2 problem # 29: Determine the maximum altitude in the sky of the Moon as seen from a latitude of 40° North. The orbit of the Moon is tilted 5° from the ecliptic.

  7. Example Solution What is being asked?...Maximum altitude of the Moon from 40° North latitude. What information is given?...latitude = 40° N Tilt angle of Moon from ecliptic = 5° Tilt angle of ecliptic from celestial equator = 23.5° Equation(s) to use: Refer to diagram two slides back. The altitude of the celestial equator above the local horizon is 90° - Latitude CE = 90° - 40° = 50° Maximum altitude of Ecliptic = CE + 23.5° = 50° + 23.5° = 73.5° Maximum altitude of Moon = EclipticMax + 5° = 73.5° + 5° = 78.5°

  8. Time and Astronomy The 24 Hour Day? One rotation of Earth = 1 sidereal day23 hours 56 minutes 4.091 secondsThis is the time required for the Earth to complete one rotation with respect to the fixed stars

  9. As the Earth rotates it also moves around the Sun. So, for the Sun to return to the same place in the sky the Earth must rotate a little more than one complete rotation

  10. Noon–to–noon isn’t always 24 hours

  11. The Mean Solar Day is exactly 24 hours. It is the time between meridian transits of the Sun averaged over four years

  12. The Year 1 orbit around the Sun = 365.2564 daysThe sidereal year 1 Tropical Year = 365.2422 mean solar daysThe time from Vernal equinox to Vernal equinox

  13. Pope Gregory XIII’s Calendar The Gregorian Calendar (1582) Most years have 365 days Years evenly divisible by 4 have 366 days except century years. Only century years evenly divisible by 400 are leap years

  14. Precession of the Equinox Like a spinning gyroscope, the Earth precesses. The period of the precession is 25,920 years

  15. The Precession of the Equinox leads to a shift of the celestial pole

  16. It also shifts the constellations of the zodiac

  17. The Lunar CycleSidereal versus Synodic

  18. The sidereal period is the orbital period with respect to the “fixed” stars: 27.32166 days

  19. The Synodic period is the length of the cycle of phases 29.530589 days

  20. Since the angular size of the Sun and Moon are almost the same, eclipses occur

  21. The Saros Cycle is an eclipse cycle 223 Synodic Months or 18 years 11.3213 days

  22. The Saros Cycle is the repetition cycle of eclipse

More Related