Special Fire (SF) or Starfish sites were just one part of the overall decoy stategy.
Other elements of this strategy were:
The Starfish sites were meant to look like fires raging at the intended target and to draw the weight of the enemy attack onto the dummy location.
The effects produced were quite sophisticated with fires differing in type, intensity and duration.
The site had means to control the fires remotely, usually from a building often (bravely) located in the centre of the dummy site.
A section of a Starfish site showing tanks of fuel and water that would be flushed onto burning straw (or other combustible material)
A 'QL' site was often located within a Starfish site and, by means of apparently careless blackout lighting, would attract the enemy bomber force away from its intended target.
By the end of the war there were 237 Starfish sites protecting 81 cities, factories and other potential targets.
Unsurprisingly, there are very few images of these secret installations
The above shows a typical site spread out over several fields
Some Starfish installations were more successful than others.
There are reports of a spectacular success being achieved on April 17-18th 1941 when Portsmouth was raided and 90% of the bombs aimed at the city fell on the Starfish decoy site on Hayling Island.
However, other sites record receiving very few bombs and postwar investigations of a reportedly successful site found no bomb craters.
Overall it is considered that 5-10% of German bombs fell on decoy sites.