I remember reading a Rashi that says that the Jews will be revered for their knowledge of the stars. What's the location of this Rashi?
Probably (though you can never be sure with questions like these) you're referring to Rashi's comments on "כי היא חכמתכם ובינתכם לעיני העמים", "this shows your wisdom and understanding in the eyes of the nations" (Devarim 4:6), where Rashi quotes the Gemara in Shabbos (75):
איזו חכמה ובינה שהיא לעיני העמים הוי אומר זה חישוב תקופות ומזלות
What is wisdom and understanding that is 'before the eyes of the nations' (i.e. appreciated by non-Jews)? This is the determination of time periods and constellations (i.e. astronomy)