Did you read the thread from start? If not, do so when you have time...
Some key points I would like to say, please don't take it as I am offending.
* The photographs for the exercises should be a fresh one, not from your archives/collection
* Author has suggested to use normal focal length (~50mm) for the exercises and to use black and white when learning.
Do you have this book? If not get it, it will be better to follow.
About the photographs you posted. It's not just moon/sun in the photograph. How you put the moon or sun in the frame with other elements in it and how a small object (when we shoot moon/sun @ 50mm it just fills a very small amount of space in the photograph) can be a dominant subject in a photograph. Not zoomed all the way in...