- Celestial Equator
The celestial equators is the projection of the Earth's equator onto the sky. The declination coordinate is an angle measured with respect to the celestial equator.
http://www.earthvisions.net/bcp/sphere/celequator.htm
(Added: Sun Oct 27 2002)
- Celestial Sphere
How do astronomers keep track of the sky when the earth is constantly moving? They use star charts that are maps of different regions on the celestial sphere.
http://astrosun.tn.cornell.edu/courses/astro201/cel_sphere.htm
(Added: Wed Oct 23 2002)
- Celestial Sphere
It is useful when discussing objects in the sky to imagine them to be attached to a sphere surrounding the earth. This fictitious construction is called the celestial sphere.
http://csep10.phys.utk.edu/astr161/lect/celestial/celestial.html
(Added: Wed Oct 23 2002)
- Celestial Sphere Java Applet
What you see in the sky depends on your location on the Earth. Use this site to create view of the sky for your location.
http://www.pcsapo.com/csphere/csphere.html
(Added: Wed Oct 23 2002)
- Ecliptic
The ecliptic is the plane of the Earth's orbit around the sun, so named because eclipses of the sun and moon can occur only when the Moon (whose orbit is closer to the plane of the Earth's equator instead of its orbital plane around the sun) crosses this plane. Because of precession, the position of the ecliptic plane changes slowly over time and so must be specified together with an epoch, usually defined as 1950.0 or 2000.0.
http://www.earthvisions.net/bcp/sphere/ecliptic.htm
(Added: Sun Oct 27 2002)
- Ecliptic, the Path of the Sun
This site provides a good definition of the ecliptic and the celestial sphere.
http://www-istp.gsfc.nasa.gov/stargaze/Secliptc.htm
(Added: Sat Oct 26 2002)
- Equinoxes and Solstices
The Royal Observatory of Greenwich provides this explanation of the equinoxes and solstices.
http://www.rog.nmm.ac.uk/leaflets/seasons/equinox.html
(Added: Sun Oct 27 2002)
- Equinoxes and Solstices
This site provides a description of the solstices and equinoxes.
http://pegasus.phast.umass.edu/a100/handouts/solstice.html
(Added: Sat Oct 26 2002)
- Introduction to the Celestial Sphere
See how the celestial sphere can help you understand our view the stars, the Earth's Tilt, the motion of the Sun and the Moon, and much more.
http://inkido.indiana.edu/a100/celestialsphere.html
(Added: Wed Oct 23 2002)
- Powers of 10
View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida.
http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/
(Added: Thu May 29 2003)
- Rising and Setting of Stars
Find out what causes stars, the Sun, the Moon, and planets to appear to rise and set.
http://www.star.ucl.ac.uk/~idh/STROBEL/nakedeye/nakedeya.htm
(Added: Sat Oct 26 2002)
- Seasons
There is a popular misconception that the seasons on the Earth are caused by varying distances of the Earth from the Sun on its elliptical orbit. This is not correct. One way to see that this reasoning may be in error is to note that the seasons are out of phase in the Northern and Southern hemispheres: when it is Summer in the North it is Winter in the South.
http://csep10.phys.utk.edu/astr161/lect/time/seasons.html
(Added: Sun Oct 27 2002)
- What causes seasons?
The seasons have nothing to do with how far the Earth is from the Sun. If this were the case, it would be hotter in the northern hemisphere during January as opposed to July. Instead, the seasons are caused by the Earth being tilted on its axis by 23.5 degrees.
http://www.crh.noaa.gov/fsd/astro/season.htm
(Added: Sat Oct 26 2002)
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