Can I pursue M.Tech in Aerospace after successful completion of B.E Computer Engineering????

Yes, you can do M.Tech in Aerospace engineering after doing B.E in computer science but you need to have a First class or 60% marks (55% for SC/ST) in B.E in computer science

You should have valid GATE score in disciplines to take admission in top colleges like IIT's and other universities

Different specializations of Aerospace Engineering are:--
Astrophysics
Aerospace Propulsion
Aerospace Structure
Aerodynamics

List of some of the best Aerospace / Aeronautical colleges in India
Siddhartha Institute of Aeronautical Engineering and Information Technology
Guru Gram Institute of Aeronautical Engineering & Technology
Hindustan College Of Engineering
Hindustan Institute of Engineering Technology
IIT (Indian Institute of Technology), Powai, Mumbai 400076
Indian Institute of Aeronautical Engineering, Dehradun
Indian Institute of Technology, Chennai
Institute of Aviation Technology
Institute of Information Technology & Management’s Aeronautical Engineering Training Academy
Mohamed Sathak Engineernig College
Nehru College of Aeronautics & Applied Science
Park College of Engineering and Technology
Rajasthan Vidhyapeeth (Deemed)University
VSM Aerospace
Academy Of Aerospace & Aviation, Swadesh Bhawan
Guru Gram Institute of Aeronautical Engineering & Technology
Hindustan Electronics Academy
IIT (Indian Institute of Technology)
IIT, Kanpur 208016, (Uttar Pradesh)
Indian Institute of Aeronautics
Institute of Aeronautical and Marine Engineering
Madras Institute Of Technology
National Institute of Aeronautical Engineering
National Institute of Aeronautical Engineerin
Punjab Engineering College