a1 02 celestial sphere

The Celestial SphereLACC: §3.2, 3.5, 3.7

• Coordinates--Declination ↔ Latitude,

Right Ascension ↔ Longitude

• North and South Celestial Poles, Celestial Equator, Ecliptic

• Using the stars to navigate

What is out there?

Wednesday, February 10, 2010

Earth Coordinates

http://www.passivesolarenergy.info/




Earth Coordinates

• North and South poles

• equator

• latitude

• longitude

• axial tilt = 23.5°

• Arctic Circle, 66.5°N

• Antarctic Circle, 66.5° S

• tropic of Cancer, 23.5° N

• tropic of Capricorn, 23.5° S


Celestial Coordinates

http://visual.merriam-webster.com/astronomy/astronomical-observation/celestial-coordinate-system.php




North Celestial Pole

http://astro.unl.edu/classaction/images/coordsmotion/startrails.html




Celestial Coordinates• North and South

celestial poles

• zenith

• meridian

• celestial equator

• ecliptic plane (Earth’s orbit, Sun’s Path)

• spring and autumnal equinox (20 Mar., 22 Sept.)

• summer and winter solstice (21 June, 21 Dec.)

• right ascension [RA]

• declination [dec]

http://astro.unl.edu/classaction/animations/coordsmotion/radecdemo.htmlCelestial-Equator (RA/Dec) Demonstrator

http://astro.unl.edu/classaction/animations/coordsmotion/celhorcomp.htmlRotating Sky Explorer

Los Angeles: Latitude: 34° 05', North. Longitude: 118° 22', West


http://astro.unl.edu/classaction/animations/coordsmotion/radecdemo.html






NavigationIf you know the declination of an object, and you measure it’s altitude when it’s on the meridian, then you can determine your latitude.Finding latitude with the Pole Star

Imagine yourself standing at night at point P on Earth and observing the pole star (or better, the position of the north celestial pole, near that star), at an elevation angle λ above the horizon.

The angle between the direction of the pole and the zenith is then (90°–λ) degrees. If you continue the line from zenith downwards (see drawing) it reaches the center of the Earth, and the angle between it and the Earth's axis is also (90°–λ).

Therefore (as the drawing shows) λ is also your latitude.

http://www-istp.gsfc.nasa.gov/stargaze/Snavigat.htm

P




Movement of the Celestial Sphere

The celestial sphere isn’t what is moving. (Of course, a spherical shell of stars doesn’t even exist.) The earth rotates inside of it.

Objects in space appear to “rise in the East and set in the West”. One can imagine why people thought the Earth was fixed in space, and the celestial sphere rotated around it--we don’t feel the Earth rotating. Actually, the earth’s rotation makes it appear that objects in space move from east to west over the course of the day and/or night.

Imagine a globe inside a celestial sphere.Wednesday, February 10, 2010

AstroTeam Classwork

• Fill in this table with these four answer choices: latitude | longitude | right ascension | declination

North/South Location

East/West Location

Earth’s Surface

Celestial Sphere

• You wake up with no memory of who or where you are, but it is night and you recognize the North Star (Polaris, the star in the tail of the Little Dipper). If the Polaris is at zenith, where are you? What if it is on the horizon? What if it is at an altitude of 23.5°?


LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.

• Ch. 3, pp. 82-83: 1, 9.

Due on the first class of the following week, at the beginning of class.


Celestial MechanicsLACC: §3.2, 3.5, 3.7

• Marking Time: day ↔ rotation, year ↔

revolution

• Effects of the Sun: solar vs. sidereal, seasons

• Changes in the Sky: Moon Phases, Eclipses

What is going on out there?


Time -- Time Zones


Time -- Days

Sidereal Day Solar Day

23h 56m 4.09s 24h

The time between a

star’s zeniths

The time between our sun’s zeniths


Time--Year and Seasons

http://astro.unl.edu/classaction/animations/coordsmotion/transitmovie.htmlTime-Lapse Season Demonstrator

http://astro.unl.edu/classaction/animations/coordsmotion/eclipticsimulator.htmlSeasons and Ecliptic Simulator

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.htmlDaylight Hours Explorer

http://visual.merriam-webster.com/earth/meteorology/seasons-year.php


http://astro.unl.edu/classaction/animations/coordsmotion/transitmovie.html

http://astro.unl.edu/classaction/animations/coordsmotion/transitmovie.html

http://astro.unl.edu/classaction/animations/coordsmotion/eclipticsimulator.html




http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html

http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html





The Earth-Moon System: Moon Phases

http://www.astrosociety.org/education/publications/tnl/12/12.html

http://astro.unl.edu/classaction/animations/lunarcycles/lunarapplet.htmlLunar Phase Simulator

http://astro.unl.edu/classaction/animations/lunarcycles/moonphases.htmlThree Views Simulator






http://astro.unl.edu/classaction/animations/lunarcycles/lunarapplet.html

http://astro.unl.edu/classaction/animations/lunarcycles/lunarapplet.html

http://astro.unl.edu/classaction/animations/lunarcycles/moonphases.html

http://astro.unl.edu/classaction/animations/lunarcycles/moonphases.html

The Earth-Moon System: Lunar Eclipses

http://hyperphysics.phy-astr.gsu.edu/hbase/solar/lunecl.html

http://astro.unl.edu/classaction/animations/lunarcycles/eclipsetable.htmlEclipse Table






http://astro.unl.edu/classaction/animations/lunarcycles/eclipsetable.html

http://astro.unl.edu/classaction/animations/lunarcycles/eclipsetable.html

The Earth-Moon System: Lunar Eclipses

http://astro.unl.edu/classaction/images/lunarcycles/lunareclipse.html

http://astro.unl.edu/classaction/images/lunarcycles/lunareclipse2004.html










The Earth-Moon System: Solar Eclipses

http://astro.unl.edu/classaction/images/lunarcycles/solareclipse.html

http://astro.unl.edu/classaction/images/lunarcycles/solareclipse1999.html




















The Earth-Moon System: Solar Eclipse

http://astro.unl.edu/classaction/images/lunarcycles/solareclipse1999mir.jpg


http://astro.unl.edu/classaction/lunarcycles.html




















AstroTeam Classwork

• What are two ways the 23.5° tilt of the Earth’s axis causes summers in the United States to be warmer than the winters? (Voyages, Ch. 3, pp. 82-83: 5)

Due presently.


LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.

• Ch. 3, pp. 82-83: 11, 16.

• Ch 4: Tutorial Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due on the first class of the following week, at the beginning of class.


http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19






a1 02 celestial sphere

Education

celestial coordinates

celestial coordinates

north celestial pole

celestial mechanicslacc

celestial equatordec

earth coordinates north

celestial sphere lacc

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