I am applying for graduate programs this year. My undergraduate major is physics while my intended specialty is astrophysics. I apply for physics program for the most of schools and astronomy program for the others. One of the main factors which led me to apply for physics program rather than astronomy was the fact that there are much less student openings in astronomy graduate schools, due to its small size of department in general.
I am thinking of 4 recommenders in my mind, and three of them is faculty in astronomy (while two out of the three are theoretical astrophysicists)
I wonder how much the affiliation of recommenders would matter in the consideration of LORs. i.e. Do you think it is `inappropriate' to apply for physics graduate school with three letters from astronomy faculty?
(This concern recently came up with since I read the requirement of one physics program that at least two of the LORs should be from professor in physics.)