The Richat Structure, also known as the Eye of the Sahara and Guelb er Richat, is a prominent circular feature in the Sahara desert of west–central Mauritania near Ouadane. This structure is a deeply eroded, slightly elliptical, 40-km in diameter, dome. The sedimentary rock exposed in this dome range in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges.
From the photographer on reddit: its a composite image of 7 photos taken with 15 second exposure on each. and like “kevyB” posted, the shoreline was post-processed in photoshop. EDIT: also “biga29” was correct in stating that there was a Type of tripod used to rotate opposite of the earth’s rotation, to cancel out the star trails.