AT A GLANCE it looks like a semi-pleasing printing error. Or a photo taken by mistake, filled with claustrophobic depth of field, shadows and murk – like so many accidental ‘closeups’ of the inside of a camera bag. But to those who know what they are seeing, this image bears a distinctive visual fingerprint shared only by a relative handful of others. And its makers believe this could be the most remarkable example of all.

The lines climbing the image are a recording of the sun’s path across the sky, rising and falling with the seasons. Eight full cycles of them, in fact – exposed through a pinhole aperture onto a piece of photographic paper inside a cider can, which almost a decade ago was pointed at the horizon and attached to a dome at University of Hertfordshire’s Bayfordbury Observatory. Then forgotten about.

The camera was rediscovered in September this year by a technician, and the image inside successfully retrieved. Now, it’s believed that at eight years and one month, it could be the longest photographic exposure ever made.[…]