Which college is better among IIT and NIT for astronomy?

Here I suggest you a site for your question https://www.quora.com/Are-there-any-IIT-institutes-for-astronomy-astrophysics.

There are not many colleges to choose from, for courses in Astronomy. Please refer to the link provided below which contains top colleges for courses in Astronomy in India. You should be able to decide which college is better, using the filters on the page. https://www.shiksha.com/science/colleges/a