Among special classes implemented in academic years of 2013 to 2016 at Faculty of Education, Wakayama university for second grade students of Attached Junior High School of Hidaka Senior High School,the class implemented in 2015 which utilized the astronomical observatory atop the faculty building is reported. The class was about phases of Venus which is one of the contents for third grade of junior high school, using the real-time movie of Venus taken at the observatory. The purpose of the class was that Venus actually has phases, and whether the class surely conveyed the purpose is examined through students’answers of the questionnaire taken at the end of the class.