Respected Dr. Shabbir. I would certainly like to reply to the followers of Zorostrainian religion that Muslim prayer can never mean what he is thinking of. Allah Almighty has created Sun, Moon and Stars with a purpose.
فالق الاصباح وجعل الليل سكنا والشمس والقمر حسبانا ذلك تقدير العزيز العليم
6:96He is the Cleaver of the daybreak. He has appointed the night for stillness, (rest and tranquility) and the sun and the moon to run their well-calculated courses. They become means of calculating time for you (10:5). Such is the Design of the All-Powerful, the All-Knowing.
So the keeping the track of the time because of "Sun" doesn't mean, that Muslims "worship Sun"!