How dark is too dark to sail?

Well finally the wind came back today, typical that I had to stay late at work and even when I managed to get home in time to catch the last glimps of daylight I realised that I had left my harness in Liz's car! Luckily it wasn't long before she arrived home and I managed to get out at dusk. Was great just to be on the water and tomorrow looks quite good by Amwaj standards...