Star and sundial by Anthony Sneewins, 1681.
© Science Museum / Science & Society Picture Library
This astronomical instrument was made by Anthony Sneewins, an instrument maker from Delft in Holland, and is believed to be a joint star and sundial for finding local time. In use, the instrument is held vertically by the ring and rotated until the Sun can be aligned with the moving sighting vane. The position of the vane gives an indication of the Sun's altitude and hence the local solar time. This instrument is transitional from the traditional astrolabe that was disappearing in Western Europe and being replaced by instruments such as the ring dial and horary quadrant. This view of the device shows the sundial part of the instrument which indicates equal hours.