Well AG has really thought of how the script should be when he named each character. Arun means Sun, Chand means Moon and Tara means Star.
Sat's epi was poignant one. Colonel finally sees the body of his wife. His denial of all the years that Tara has not died come to rest. He understands what his wife was trying to tell him all along. Yes she is no more in body with him. But her spirit is always with Chand, the boy who treated her like his own mother. He has to learn to see her in Chand. Tara is always with him. In other words it is not time for colonel to join her. He has to take a different role. He has mentored Chand well. It is time he gave up his legacy to the youngster and stand as a pillar of support for him as he scales new heights.
Understand that Moon and Star is always together in the sky during night. They come after the sun set. Setting doesn't mean the end. Sun has to come next day to do the same duty. Setting just means handing over the responsibility of lighting at night to Chand or Moon.
Colonel understand it and rightly hands over the mantle to Chand telling he has full trust on him. It is also a message to all parents and teachers that after a certain time they have to step back and give youngsters the chance. They have to trust that they have given the right value to the youngster to take charge rather than micro manage them.
It is always nice to hear Chand the son of Colonel Abyankar than colonel Abyanker father of Chand. Because in the former the glory is carried forward to the next generation and only when you hear the former you understand your success as a parent or teacher.