Astronomer Jack Robinson from the University of South Florida has further proposed that cairn pair FD was used to observe the rising of the star Fomalhaut, which would have lined up with its rising point between AD 1050 and AD 1450, when Fomalhaut had its first heliacal rise roughly a month before the summer solstice. A carbon date for the Bighorn Medicine Wheel comes from a piece of wood found in cairn F, corresponding to an age of no more than 220 years, roughly in the middle of the 18th century. However, this date can only be considered as a minimum age, as the wood may have become lodged in the cairn after construction. Stated by Don Grey in his, "Summary Report," page 317 of the 1958 Wyoming Archaeology Society's excavation of the Wheel, "In the large cairn on the northwest side of the structure was found a piece of wood pinned down between the courses of stone in the wall. A sample was taken…for dating."