Oxford Dictionary of Astronomy
 Ian Ridpath. 536 pages of definitions and explanations on astronomy terms

The Dictionary of Space Technology
Joseph A Angelo, Goes through all the terms and word used in space technology, focuses on the space shuttle and Apollo  program. Ideal for some interested in space mechanics and technology.

Star Names, Their Lore and Meaning
Richard Allen, While not strictly a dictionary, it does go through every starname you can think of and explains the history of the name and alternate names for them. It does this by constellation, which are listed alphabetically.