The Sky at Night celebrates its 800th episode while filming takes place under the coronavirus lockdown.Chris Lintott explores how some astronomers are managing to continue making observations by controlling telescopes as far away as Hawaii from a laptop in their bedrooms in Belfast. Maggie Aderin-Pocock investigates how members of the public can get involved in analysing data from Mars, even when they are confined to their homes. And Pete Lawrence points out some treats in the night sky that we can all see if we keep looking up even when we're locked down.Plus a treat from the archives of the last 799 episodes set to a specially commissioned new arrangement of the show's famous theme tune.