In my opinion his drawings are more of a goal than a how-to illustration. I am guilty myself of copying his drawings but I don't think it's helpful. He has his own visual language, as we all do. He has translated life drawings into his language. Copying his language is like trying to learn how to speak English by copying a great work of literature over and over. So I feel he's showing us more of what the results of life drawing could be than actually wanting us to copy his drawings. Take what he says, compare it to his own drawings, and then apply it to your life drawings. I think you'll get a lot more out of it that way.
"Astronomy offers an aesthetic indulgence not duplicated in any other field. This is not an academic or hypothetical attraction and should require no apologies, for the beauty to be found in the skies has been universally appreciated for unrecorded centuries."