A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2020 Jan 29, 11:36 -0800
Frank You wrote: there's one terrible arithmetic error in the article which someone should have caught. See the attached image from the article. Do the math! I would guess that most NavList readers, even those unfamiliar with lunars specifically, will spot this big mistake.
I'm not sure about the 13.2°/ day. It's a bit above my pay grade. My simple mind said 360/28 = 12.9°/day, but I wasn't allowing for Earth orbit. However, isn't the author slipping between minutes of arc and time a little carelessly? 3.3 minutes of Moon arc is six minutes of time, true, but six minutes of time is 90, not 6 minutes of E-W arc. I.e. or 90nm along the Equator.
You also wrote: do you really count Maskelyne as a "great man"? It seems we're in the midst of a reactionary phase.
Poor old Rev Dr M got a poor reputation amongst less informed circles after Sobel's 'Longitude' was published, so it's always rather pleasing when we read that he was, in fact, a man with many good attributes.
You also offered some pretty strong comments concerning reproduction sextants etc, probably eminating from the Far East. Not withstanding the fake nature, some of these craftsmen manage to produce some extremely pretty items. Has any reader ever bought an example out of curiosity to see if it was anywhere near useable in a very rough and ready sort of way. I bought a Sun dial and a box sextant, because I wanted to get an idea how they worked. Neither did. The Sun dial went straight back; the gnomon wouldnt stand up straight. I kept the box sextant in case anyone asked me what one looked like. It's probably worth its weight in brass alone. Unfortunatey, the quality of its inside doesn't match the attractiveness of its outside. DaveP