So this is di minus the focal length. As simple as that. The formula to calculate the focal effective focal length is f d 2 tan a2 where.
Used in our 1000mm focal length telescope this formula produces a FOV of slightly over 12 degrees 212 1000 00212 573 121476.
Calculate the Focal Length. Photo by PeopleImages via iStock. The formula for determining the focal length of any lens is. Used in our 1000mm focal length telescope this formula produces a FOV of slightly over 12 degrees 212 1000 00212 573 121476.