Moonlight at or near full moon is a significant source of light.

The painter was an ancestor---the great great grandfather of Sherlock Holmes (see Wikipedia: Claude Joseph Vernet: Literary references).

Credit/Permission: Claude Joseph Vernet (1714--1789), 1771 (uploaded to Wikimedia Commons by User:JarektUploadBot, 2011) / Public domain.
Image link: Wikimedia Commons: File:Joseph Vernet - Night - Seaport by Moonlight - WGA24731.jpg.
Local file: local link: moonlight_vernet.html.
File: Art_m file: moonlight_vernet.html.