The Wapiti or Elk group is from the Hall of North American Mammals at the American Museum of Natural History (1941). The background painting is by James Perry Wilson. Michael Anderson, the Wilson scholar who is based at the Yale Peabody Museum, wrote to me quoting a letter from Wilson where he is describing how he projected a slide he had taken of the moon so that it was three-foot by two foot on the wall. The moon came out three and an eighth inches in diameter. He notes that this is the same size as in the moon he painted in the Wapiti diorama (above). Michael asked me to calculate the focal length of the lens Wilson was using and therefore, working with Wilson’s projection method, calculate if the moon was the correct size in the diorama. The lens turned out to be 300mm, something Michael was later able to corroborate from notes on some of Wilson’s moon slides. From this and working out the depth of the diorama where the moon is painted from a scale drawing, I calculated that Wilson had painted the moon 50% too large. The picture above is rather small, but you can see the moon just above the horizon next to the tree in the left foreground. Wilson was fastidious about such things, so the discrepancy needed chasing. There is an optical anomaly called the moon illusion. When the moon is close to the horizon it appears 50% larger than when it is high in the sky. There are many theories for why this is, but there is consensus on the 50%. There are no notes from Wilson about this, but my speculation is that this is the reason why Wilson painted the moon this size.
Anyway, it is a stunning diorama and is looking wonderful after a spring clean (if a little over lit).
Look in the earlier Diorama posts for suggestions on how to view 3D pairs of photographs.