I am trying to find out the value to enter in the diameter field under the telescopes tab for a photo lens. When I search on lens diameter for a specific lens, I get results on how to determine the filter size. Is that the same as the lens diameter? On some of my lenses, the lens diameter looks quite a bit smaller than the filter thread diameter. I would like to be able to simulate what images would look like using a camera lens in addition to of a telescope.