The annual Observer's Handbook (2021: ) can be found in observatory control rooms and astronomers' reference shelves worldwide. Published in the autumn of the year, the 352-page Handbook contains detailed information on astronomical events in the upcoming year and is an in-depth reference of significant astronomical data such as observing techniques, physical constants, and optical properties of telescopes. The first two editions were published in 1907 and 1908, respectively. For the following two years information from the Observer's Handbook was integrated into the main Journal, but it was decided eventually that the Handbook return to circulation. The 3rd edition of the Observer's Handbook was published in January 1911, with Editor C. A. Chant aiming to publish the 1912 edition in the autumn of that year. The 110th edition was published in 2017, covering events in 2018. In addition, for the first time, a USA Edition was created for the American audience, in cooperation with the Astronomical League. The publication is currently in its 113th edition published in 2020, coving the events of 2021.