In May of this year, I was hired as crew to assist in the delivery of the 110-foot Kingship Marine-built Relentless from Fort Lauderdale, Fla., to Montenegro via Bermuda and Faial in the Azores. Across the Atlantic Ocean, down the Mediterranean, into the Adriatic it was quite the passage aboard a stout ship, with mostly fair weather, a happy crew and a trustworthy skipper.
Although I have plenty of sea time and had completed a trans-Atlantic passage 50 years ago aboard a 70-foot ketch, much of that sea time has been in schooners moving to and from New England to Bermuda and the Caribbean. Most, if not all of those passages, were done before GPS when navigation was celestial with assistance from radio direction finders (RDF), and LORAN. Low-tech gear by today’s standards, but effective, virtually trouble-free and elegant. Especially the celestial.
Standing on the bridge of Relentless, where multiple radar screens, GPS receivers, AIS transponders, computer keyboards – a virtual bevy of electronic devices – made me feel as if I were on the bridge of the Starship Enterprise. It was intimidating, but the captain and crew put me through my paces, so by the end of the passage, the electronics were, if not friendly, at least less alien.
I had been hired by captain Steve Steinberg, with whom I had sailed before, as “an analog replacement for electronics.” He wanted me to do daily celestial navigation and plot positions on the chart. He was hoping the crew would be introduced to some older navigation techniques. He’s correct in wanting to have crew become more familiar with navigation systems that aren’t reliant upon GPS. The U.S. GPS system is outmoded and in need of modernization, with no backup system in place. GPS signals being hacked by unfriendly nations creates confusion and danger and is becoming more commonplace.
During the course of a five-week passage, I could take reliable observations of the sun and the moon. I was less successful with star sights, mostly because of the ship’s motion. I used the GPS as a “master teacher,” taking the GPS position as my DR when taking sights. I also used my Celesticomp V calculator to assist in the math. I took multiple observations and using the Celesticomp eliminated the necessity of creating an assumed position. I was more concerned with getting as many observations as possible than I was with the procedure of sight reduction, with which I am familiar.
For the sake of this navigation problem, though, we will be using the analog methods found in HO249 and the Nautical Almanac.
We will be doing a lower-limb observation of the moon. The day in question is May 26.
The height of eye is 15 feet. The dead reckoning position, N 40° 25’ by W 18° 40’. The time of the observation is 05:35:15 GMT.
The Hs of the lower limb of the moon is 14° 35.8’.
1. Find the HO.
2. Find the LHA.
3. Calculate the intercept.
4. Plot. n
For answers go HERE