Slide 53
NASA. The NASA site contain many useful information and images.
Wikipedia. Note: The Wikipedia is probably the quickest way to find information. However, because it can be edited by anyone, one should not trust the information without checking independent sources or risk getting wrong or misleading (intentional or not) information.
HKU Physics Department, Nature of the Universe web site http://www.physics.hku.hk/~nature/
J. M. Pasachoff, Astronomy: From the Earth to the Universe (1998).
E. Chaisson and S. McMillan, Astronomy Today (2005).
J. Evans, The History & Practice of Ancient Astronomy (1998).
C. M. Linton, From Eudoxus to Einstein: A History of Mathematical Astronomy (2004).
Dr. Richard Hennig
Sources of pictures: Pictures are obtained from the following sources unless given next to the pictures.