National Physical Laboratory

Blue Sky research

The optical technologies team at NPL helped Expedia send its 'Blue Sky Explorer' to measure the colour of the sky around the world by providing a portable spectrometer, specially built for the project.

NPL's collaboration brought unforeseen benefits for the future of affordable, transportable spectrometry. Expedia's 'Blue Sky Explorer' was able to observe the world's best blue sky and unequivocally assign a set of internationally accepted colorimetric coordinates so that it could be fully defined.

Blue skies

NPL's goal for the mission extended beyond finding ideal holiday destinations to demonstrating how everything can be measured. It did not require costly or complicated equipment, just a well-defined procedure that a non-scientist could use.

The spectrometer for this experiment was built from scratch using cheap, lightweight alternatives to lab-based equipment. An LED torch replaced the costly calibration lamp and it achieved a 4 % margin of error, which is not that much different from some laboratory experiments. NPL ensured that the spectrometer was calibrated, thereby providing reliable measurements at each location. All data from the measurements made with the spectrometer was sent back to NPL via email for processing and analysis.

The world's bluest sky was found to be in Rio de Janeiro, followed by Bay of Islands in New Zealand and Uluru in Australia (Castell Dinas Bran in Wales was in ninth place and top of the three UK destinations in the top 20).

Find out more about NPL's research in Optical Radiation & Photonics

Last Updated: 10 Jan 2013
Created: 15 Oct 2010