A solargraph, like the one on this page, is a long-exposure photograph that shows the path taken by the sun across the sky, over time. In this case, the time period is the six months between the December solstice of one year and June solstice of the next. The streaks in the photos are sun-trails – the sun moving in its shifting path across the sky from day to day over that six-month interval.
The APEX telescope at the Llano de Chajnantor Observatory in Chile acquired this image over a six-month period, from about the time of the December solstice in 2009 until the June solstice in 2010. The astronomers inadvertently created art, but their original goal was to assess the quality of this site in Chile for astronomy.
The mostly unbroken sun-trails show that there were some clouds at the site during the six months — but not many. This solargraph is so sharp that holes in the fleeting clouds over Chajnantor on the few partly cloudy days sometimes managed to create individual “snapshots” of the solar disc (seen as dots in the broken sequences).
By the way, Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 meters (15,700 feet) in the Atacama Desert of northern Chile. It’s home to the largest and most expensive astronomical telescope project in the world, the Atacama Large Millimeter Array (ALMA).