Rights: The University of Waikato Published 29 July 2008 Download

The Dobson spectrophotometer at Lauder in Central Otago is a key ozone-measuring instrument used by NIWA and is part of a global network of similar instruments.


The Dobson spectrophotometer at Lauder is one of 150 worldwide that daily measure the amount of ozone present in the atmosphere. They were designed by Gordon Dobson in the 1920s, with improvements being made right through until the 1950s.

The spectrophotometer works by comparing the intensities of a pair of ultraviolet wavelengths.

One wavelength is partially absorbed by ozone and the other is unaffected. The ratio between them gives a measure of the amount of ozone in the atmosphere along the light's path.