Paul Parsons 
Deep-Sky Observer’s Year [PDF ebook] 
A Guide to Observing Deep-Sky Objects Throughout the Year

Deep-sky observing — that’s looking at the stars, nebulae and galaxies — is easily the most popular field for amateur astronomers. The big problem faced by non-professional observers is what to look at — what’s visible at a paticular time of year. The Deep-sky Observer’s Year is a month-by-month guide to the best objects to view. Objects are given a "star rating" according to how difficult they are to observe or image (i.e. photograph) with a particular size of telescope. The book includes many images produced by amateur astronomers, as well as photographs from NASA, ESA and ESO. There is also some background information about the objects that can be seen, along with lots of useful tips, hints, and resources (especially about what’s available on the Internet) for deep-sky observers.