NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude and Longitude by "Noon Sun"
From: Lu Abel
Date: 2005 Jun 7, 09:19 -0700
From: Lu Abel
Date: 2005 Jun 7, 09:19 -0700
Frank Reed wrote: > Where is this world where one crosses oceans without GPS? Are you concerned > that yours might break down? The best backup for GPS is another GPS. > Celestial navigation is no longer a primary method of navigation. There are plenty of > people who want to do it for fun and challenge and maybe, just maybe, for a > backup in case something happens to the main GPS *and* the various spare GPS > receivers. Right on, Frank! I'll bet you'll be crucified for this remark by the "you can't trust anything with electronics in it" crowd along with the "it was good enough for Lord Nelson, it's good enough for me" crowd, but you what you speak is absolute truth. I once fantasied about writing (say, to this list) a proposal for a new satellite navigation system which could be unavailable for long periods due to weather conditions, would give LOPs only for roughly 12 hours a day, and would give fixes only during very brief periods twice a day -- and then pointing out that I had described celestial navigation. > Well sure. You can do that. Consider an alternative: even the most > enthusiastic students will enjoy being able to get a good position fix on the first > day of class. So teach lat/lon by noon sun, and then move on. Here's where I respectfully disagree: In order to teach noon sights, you've got to teach obtaining the sun's declination from the Nautical Almanac for any arbitrary GMT, plus calculating LAN (which means the equation of time), plus calculating time fairly accurately (watch error, ZDs, etc) (I'm assuming you do not want to tell the student to just stand there for hours taking observations, but rather want to give him/her the enjoyment of getting a good position fix with 15~30 minutes observation. Plus they have to know all about IE/IC, semidiameters, etc, etc.... Putting it another way, the only thing NOT required for a good noon sight is LHA! But, to give the devil his due, reduction is a lot simpler. Wouldn't a shot on a bright planet at dusk be just as simple as a way of giving the student the early encouragement? A good sight reduction form should step the student through the steps, including stepping him/her through the equations for calculator reduction. (I'll admit bias -- my very first shot was of Venus at dusk. We took sights and then adjourned to a local coffee shop where our instructor helped us reduced our sights. When my LOP came out only about 1-1/2 miles away from my known position I felt like Christopher Columbus!) I was going to reply to another of Frank's postings, but I'll include my ideas here since part of this posting included comments on the variability of students "getting" celestial: I think one of reasons why people don't want to learn celestial (ignoring for the moment that today it's an anachronism) is that it seems so very complicated. But a big part of this is simply our mysterious terminology. When I open a celestial class (or even try to motivate folks completing a coastal piloting course to consider going on to learn offshore navigation) the very first thing I tell them is that it seems more scary than it really is because celestial is based on many notions they already know, but it's obfuscated by arcane terminology. Why, for example, do we speak of the GP of a body in terms of DEC and GHA instead of L/Lo?? Speaking of the challenges of teaching: I'm an engineer. I've always lived and worked where there have been a high concentration of engineers. I've taught USPS's coastal piloting courses for over two decades. Teaching a mixed audience the concepts of allowing for currents is always a challenge. The engineers in my class see it instantly as a simple problem in vector math and are ready to move on; the others are totally mystified and I have to figure out how to explain current diagrams to someone who last took high school math 20 years ago and hated it! Lu Abel