“For common purposes we may without sensible error suppose the earth's motion equable and neglect the corrections, and then the rule for the parallax of {{w|right ascension}} will be this:Sine lat. : rad. : : cotang. A : cotang. C, or rad : sine lat. : : tang. A : tang. C; then long. star \mp C = long. of λ.Cosine C : cosine A : : semi transverse axis : z.And cosine decl. cosine (ʘ - λ) :: z : x = parallax of right ascension.”