Text ( visual ) : unmediated The monthly sky guide / Ian Ridpath and Wil Tirion. -- 2nd ed. -- Cambridge ; New York : Cambridge University Press , 1990. -- 63 p. : ill. (some col.) ; 30 cm. -- Includes index. -- ISBN 0521386659 ; (BA66338861) ; https://ci.nii.ac.jp/ncid/BA66338861 Author Heading(s): Ridpath, Ian ; Tirion, Wil. -- Classification(s): LCC : QB63 ; DC20 : 523.8/022/3. -- Subject Heading(s): LCSH : Stars -- Observers' manuals