To Mcaminos from manxcat,
Martin, Your post to me [above] answered some of my basic questions about bubble-octants / sextants vs. marine sextants. Thanks. It’s just that this subject is difficult to explain in writing. It would more understandable in person using a bubble or natural horizon sextant to demonstrate. This of course, would be the preferred instruction technique (incidentally, the face-to-face, hands-on method is the only way I personally would attempt to learn celestial navigation). In my reading on this subject I understand that the natural horizon marine octant was an earlier, more primitive, version of the later more-advanced marine sextant[?]
Your comments taken on the whole make the bubble versions seem far superior to the standard natural horizon marine sextant[?] I would’ve thought the same thing. However, also in my celnav reading, I came across the vintage book, “The Wilderness Route Finder: The Classic Guide to finding Your Way in the Wild”, by Calvin Rustrum [University of Minnesota Press, Minneapolis 1967 & 2000]. In this book, the author states that the natural horizon, whenever it is visible, is much preferred to the bubble horizon; and apparently, even the maritime sextant using the two pots of reflective liquid placed on the ground–are preferred to the bubble-octant / sextant’s horizon which is the least preferred method for land navigation. When navigating on land there are permanent landmarks that enable triangulation using surveyor’s instruments (i.e. transits). This would be a big issue for me, because I live in the mountains, and don’t have easy access to nautical horizons. I am going to keep referring to the explanation in your previous Email regarding the angles of degrees in octants and sextants, and see if I can get it straight.