From how many colleges one can do BSc in astronomy
There are many colleges available in India which offer B.Sc in Astronomy so you can consider any one of themas per your interest and convenience -
JNTU College of Engineering, Hyderabad
Indian Institute of Astrophysics, Bangalore
Osmania University
Indian Institute of Science, Bangalore
Birla Institute of Technology & Sciences, Pilani
Punjab University
Institute of Fundamental Research, Tamil Nadu
Astrophysics, Tata Institute of Fundamental Research, Pune etc.
Hope this helps!!!