Brian nice telephotos, I shot photo's like that the summer of 70 onboard a US Navy reserch ship in the South Pacific, laying on my back using a 500mil.lens plus 2 doublers and a trippler of a foreign nation cargo plane over flight of our ship. Turned out to be a one of a kind late 40's early 50's prop plane. Its crusing altitude was about 20k + guessing as there was nothing to refernce its altitude other than the Jane's Aircraft book that a certain Officer luckily had.