AlieOS

They haven't done pre-boarding for any oasis class ships since the restart. You cannot make most reservations, some specialty dining/MTD, until connecting to the ships Wi-Fi. Even so prior to the restart you weren't allowed to start booking online until 30 days before sailing. 

The upper pool deck level (deck 16) might be good although there are a lot of lights on the pool deck.
Solarium bridge wings or the back of the sports deck could be good options too. I like stargazing from the helipad, but unfortunately there is no guest access to the helipad on Oasis Class ships.