A full moon peeks out from behind some clouds, illuminating a path along the sand dunes at Merthyr Mawr. The whole scene is filled with a silvery light. Notice how the shadows are tinged with lilacs and greys. The sand dunes at Merthyr Mawr are the size of about 340 rugby pitches (840 acres), and is home to the biggest dune in Wales – the Big Dipper.