NavList:

Frank,

This is clever indeed!  I had to think hard about why it works.  Perhaps it’s because the Sun and the tip of one’s shadow are antipodes on the celestial horizon of a highly localized celestial sphere centered on the top of one’s head.  No ‘height-of eye’ correction is needed; but, perhaps, a ‘depth-of-eye’ correction might be required by the observer’s eye placement ‘half-a-head’ below the plane of the celestial horizon.  Thought I might rig an ‘over-the-head’ device with eye-level, left and right horizontal protrusions and thus provide shadow points for which neither ‘height-of-eye’ nor ‘depth-of-eye’ corrections would be needed.

It occurs to me this might account for a rather odd bit of British naval attire: the ‘thwart-ships’ style hat.  It never seemed (to me) to be very practical: it catches the wind and leaves its wearer facially exposed to sun, salt spray, heavy rain, and driving snow.  However, it would seem to be particularly well suited to shooting anti-lunars.  It doesn’t need to be reversed when taking a sight and its eye-level ‘wings’ result in convenient antipodal shadows.

Captain James Cook (shown in the attached Madame Tussaud’s depiction) seemed particularly fond of lunars as well as thwart-ship style headwear.  Ok, I don’t want to take all this too far since there’s much about which I need to be corrected; however, I now have much greater respect for the navigational applicability of broomsticks and I will never, ever look at my shadow in quite the same way again.

Many thanks, Frank.  Cheers to all.

Jim Wyse

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