A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2017 Jan 10, 19:10 -0800
I would still like to know whether Frank's site does AH scenarios and indeed whether we should be using the NA intructions on AH readings for the lunar clearance.
Frank can certainly correct me if I'm wrong, but although his online clearing tool does not explicitly handle AH altitudes, there should be no reason why one couldn't use them. The altitude fields include a selection for upper or lower limb shots. As long as one corrects for index error and divides the altitude by two beforehand, it would be the same as altitudes with a natural horizon. However, since there is no selection available for center-of-body shots, altitudes of the Sun and Moon would have to be limb to limb, as opposed to overlapping shots of the type in David C's original post. (Unless one figures in semi-diameter in advance, also.)
As for the corrections in the NA: I would need to investigate more to be certain. But, given that the tables (used as described in my previous post) yielded a very similar result as calculating the refraction and parallax directly, and given that Frank's "Easy Lunars" page describes a similar process, I would say yes, that is a viable method. The only difference being that one needs to subtract 30' for a limb shot as opposed to 15' for a center shot.
No apologies necessary for the mistakes. We all make them. Best to recognize them for what they are: an opportunity for bettering one's self. :)