Below you can find the 150 a.d.: this egyptian astronomer discovers irregularity in the moon's orbital motion Jeopardy Words Answer. The answer to 150 a.d.: this egyptian astronomer discovers irregularity in the moon's orbital motion has 7 letters. This clue belongs to the The moon category and is part of Jeopardy Word Level 1513. If you scroll near the bottom you will find other clues and answers part of level 1513