You can download Fundamental Astronomy 6th edition by Hannu Karttunen , Pekka Kröger , Heikki Oja , Markku Poutanen and Karl Johan Donner free in pdf format.
Now in its sixth edition, this successful undergraduate textbook gives a well-balanced and comprehensive introduction to the topics 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 chapters on galactic and extragalactic astronomy as well as cosmology were extensively modernized in the previous edition. In this new edition they have been further revised to include more recent results. The long chapter on the solar system has been split into two parts: the first one deals with the general properties, and the other one describes individual objects. A new chapter on exoplanets has been added to the end of the book next to the chapter on astrobiology.
In response to the fact that astronomy has evolved enormously over the last few years, only a few chapters of this book have been left unmodified.
Long considered a standard text for physical science majors, Fundamental Astronomy is also an excellent reference and entrée for dedicated amateur astronomers. For their benefit the introductory chapter has been extended to give a brief summary of the different types of celestial objects