NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Peter Ifland's "Taking the Stars"
From: Fred Hebard
Date: 2003 Sep 1, 12:09 -0400
From: Fred Hebard
Date: 2003 Sep 1, 12:09 -0400
I purchased this book, mostly to get a feel for the precision of older sextants. It was a delight to read. The pictures are spectacular. Dr. Ifland repeats the statement that the U.S. Naval Academy has discontinued its required course in celestial navigation. Apparently, the course, which had been taught since the Academy was founded in 1845, has been replaced with a modern equivalent, as people continue to maintain on this list that midshipmen are still instructed in celestial navigation. But apparently they are not instructed as thoroughly or to such length. At last these conflicting claims about the Academy abandoning instruction in celestial navigation appear to be clarified. Especially enlightening were the discussions of artificial horizons. Numerous devices were invented in the past, and Dr. Ifland appears to discuss the physical basis for all possible types of artificial horizons (Hopefully, some inventive soul will prove me wrong by coming up with a novel design). This discussion (which spans more than one chapter) should be of interest to all those interested in this subject. It was of interest to me that submariners were issued artificial-horizon sextants for use when surfaced because the conning tower frequently was too low to get an accurate view of the horizon. If the relatively stable platform of a submarine was difficult to use for an ordinary marine sextant, imagine the difficulties from a small yacht. This would appear to recommend bubble sextants to yachtsmen. Certainly bubble sextants should be adequate for all those who rely on the Air Almanac and H.O. 249. The one disadvantage I can see is that they could not double as stadimeters. As best as I can tell, the maximum precision of old pillar sextants was 5 seconds of arc. However, if they were circular sextants, this precision might be increased to about 1 second by repeated measurements around the circle. One quibble is that Dr. Ifland does not report the correct reading of most verniers which he illustrates. For instance, the scale in Figure 64 is measuring about 31d 37' or so, as best as I can determine, not 31d 34'. Likewise, the scale in Figure 65 measures 36d 15' or 16', not 36d 17'. In Figure 71, the scale reads 94d 9' 0" or thereabouts, not 94d 9' 30". These discrepancies could shake the confidence of a newcomer; I feel some degree of trepidation reporting them. It's possible Dr. Ifland read the scale, then set the instruments down to photograph them, rather than reading the scale off the photographs. I was a bit disappointed that Dr. Ifland did not discuss further the merits of various telescopes. The purpose of the various telescopes is still somewhat of a mystery to me. Overall, I was very pleased with "Taking the Stars," and recommend it highly.