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Frank,

Thank you for.your answer. I understand what you are saying on a practical point of view - I was trying to understand the theory of augmentation phenomenon and how it is calculated. This formula assumes perfect spheres, that is why Mr. Umland has further corrections for oblateness of Earth, which apply to parallax calculation.

This is in continuity of my previous thread, showing that augmentation was anyway cancelled out, since parallax was calculated after the addition of the augmented SD whereas in the American Navy method adds a non-augmented SD after parallax is calculated from the apparent H. I later found out you made a similar comment many years ago, is that right?

Eric