I'm not sure how much or if deck 8 is any better since it is directly under the deck 9 cabin. Since sun is not important on the veranda, that is good. There is no direct sunlight. we used is as a break from the sun actually. As for star gazing, you can look out over the ocean to the sky, looking straight up wasn't necessary to us, but yes - you can not look directly up. The size was great since we could get two padded chairs and a regular table plus a small side table. We could have even put a lounger there (one of the cabins below us did that). Your room steward should be able to get it for you.
There was absolutely NO NOISE!!!. It is located right at the part of the ship where the spa begins and the Aquaspa ends. There were no chairs scraping and no foot traffic. Absolutely silent. Plus there were stairs right down the hall the led directly up to that area so it was quick coming and going to the resort deck.
I loved the cabin along with the ammendities of concierge class. So much so, I just book the same cabin on the Constellation.