Karl J. Donner & Hannu Karttunen 
Fundamental Astronomy [PDF ebook] 

Fundamental Astronomy gives a well-balanced and comprehensive introduction to the various fields of classical and modern astronomy. While emphasizing both the astronomical concepts and the underlying physical principles, the text provides a sound basis for more profound studies in the astronomical sciences. The present much enlarged second edition of this successful textbook includes a host of new knowledge acquired in recent years.