The correct answer is D) in sight reductions of planet observations. Sidereal time is used for navigational purposes, specifically to enter a star finder (A), as the basis for star charts (B), and in sight reduction using Pub 249 (C). However, sidereal time is not used in sight reductions of planet observations, as planets do not have a fixed position relative to the celestial sphere like stars do. Instead, planetary observations use local mean time or universal time for their sight reductions.