Astronomy is a tremendously exciting field. I would encourage you to pursue it if you are seriously interested in it...Firstly... have real passion in it. It isn't an easy job to become a scientist in this very vast and deep field. And second most important thing, have patience. If you are doing research, you should know how to keep it cool. Try to avoid negative people saying that 'research has no future'. It has a lot of scope even in INDIA and abroad. If you have the real passion, you will see your job to be a very interesting life! It won't just be a 9-5 messy job...So You can appear for good exams like KVPY in 11th and 12th. Cracking this exam will let you apply for IISc, best research institute in the country. I highly recommend you to target it. Also you can appear for JEE and NEST and even BIT-SAT. Your prime motto should be to get into the institutes like IITs, IISERs, BITS Pilani and NISER for integrated BS-MS course. ..If you don't get it... no worries. You can still pursue B.sc from other good colleges. For this field, it's very important how well focused you are on research. You can then appear for IIT-JAM to get selected into IISc or IITs for Masters degree.