Slovenian Nautical Almanac - Part 1 - Intro

Aljoša Kocen

Some 15 or more years ago, I spent over a year and a half on board a 42500 DWT Bulk Carrier as a Junior Marine Engineer, just after finshing my Middle Maritime School education. As an Engineer, I wasn't really tought on the subject of Marine navigation. There was a class on the subject (along with other seamanship knoledge) but we barely scratched the surface, as  as Engineers we weren't supposed to know the details. It is Master's and Officers' of the Deck job to determine where the ship will go. It's the Ship's Engine Room Crew's job to make sure she gets there. I was the part of the later.

Anway, upon embarking I couldn't wait to explore and to learn the practice of finding the position the ship at sea. In the school library we had about a ton of books on the subject. And while reading them, especially the historic part, the way it evolved through the centuries, I had this romantic vision of the seafaring as such. Well, after a few weeks on board, that romantic vision literally exploded into the thin air. We had all the GPS's, and Sattelite phones, And gyro-compasses (Magnetic one was there, and was checked dailly for errors, but unless the Gyro failed, it was not in use) and UMS (Unmanned Machinery Space, with all the remote controls, and off-site alarm boxes inside our sleeping quarters). Do they use the stuff like sextant and Chronometer, and the tables and all that I read about anymore?

The answer is: They did. Not every day, but every Officer of the Deck (Ship's Mate) was obliged to train on that under Master's Standing Orders (A little notebook, that was kept on the Bridge, into which Master's orders for the day were written. We had similar Notebook in Engine Control Room). I saw the Third mate using the sextant and doing some calculation, but at the beginning I was afraid to ask, if he could "show me the ropes". And at this point I would like to express my gratitude and appreciation to the master and First mate of the Ship. Mr. Adalbert Štancar, and Peter Ivanež, respectively. Not many Masters and Mates  even allow a "Black-Gang" Junior member  up on the Commanding Bridge. I've seen some, who wouldn't even contemplate the idea, that a Junior Engineer would spend time off on a Bridge. I was one very lucky Junior Engineer. Not only was I allowed to come to the Bridge. Both Master and all the Mates were quite happy answering all my questions regarding the navigation of a ship at sea. There was even a time in the middle of the Atlantic (We were en route from Gibraltar to Tubarao, Brasil), when I was allowed to steer the ship. I must admit, that my steering was so bad, that driving a car in a similar manner would land me in jail, to say the least. But it improved over time. Even my Chief Engineer, Srečko Tramte, a 6ft tall, 220lb veteran Engineer (his first post as Ch. Engineer was in the same year I was born, in 1979), and a man to whom I still look with admiration, and have regarded  him at the time as almost like a fatherly figure (Not to mention, that the way he treated all of us, whole Engine room Crew would most likely both, kill, and die for the man)  commented once (Some years later we met in Ljubljana, when my seafaring days were already over), that he felt it was right for me to learn  as much  as I can about as much as I can while I'm doing my Apprenticeship. You only have a year to learn.  And if you don't learn, you most likely will not know. And any vessel, ocean going, or not, is a dangerous work site. Not knowing can get you mamed, or killed.

Why Celestial Navigation, when all the electronic aides are available?

In the 21st Century, when a 50$ phone has a GPS included, and downlaoding charts and maps is measured in minutes, it really makes you wonder, why on Earth would anyone settle for the Sextant and Tables? I can look at my watch and it will tell exactly where I am. The answer is simple. It is really independent of the power source. You  don't need electrical power to use it.  Besides that, GPS, GLONASS and other satelite based systems are Government sponsored. GPS is run by United States Department of Defence. And the signal is only available as long as they give one to you, or unless they pull the plug. Which they actually can, and they would if such a need arises. Thinking of it... a fully blown GPS controller, powered by, say Arduino, costs what? Franklin? Grant (These are the guys on a $100 and $50 bills)? And it is accurate to within meters. Imagine building an amateur missile and shoting it accros the city. US DoD would quickly use the kill switch on the civilian access to the positioning system. Same goes for Russian GLONASS and EU run GALILEO.

Celestial Navigation requires only one thing. Clear Sky. Nothing else. Sun, Moon, the planets and the stars are there. You just need to look at them.  We all know Polaris star, which points towrd the north. But to obtain the position of a ship at sea in a more accurate way we need the following equipment:

  • Sextant. It is used to accurately measure height of Celestial  Bodies above the horizon. 
  • Plotting Sheet. It is a blank sheet of paper with Mercator projection on it and a Compass rose. We use this to plot our Lines of position. In practice navigational chart is used. I'll show you later how to construct a simple plotting sheet yourself.
  • Chronometer.  The earth revolves around its axis as well it rotates around the Sun. Celestial  Bodies so appear to move over the sky. Knowing exact time of observation is critical (1 minute of error in time, may result in 15 Nautical miles of error in Longitude. You are either well away from Golden Gate Bridge, or already landed on Alcatraz Island).
  • Nautical Almanac. This lists periodic positions for the Sun, Moon, brighter planets, and 57 navigational stars on an hourly or daily base. It is by using these calculated numbers together with observations taken, one plots the position on the Sheet or Chart.
  • Navigational rulers, A brass divider, and a simple pencil
  • Basic mathematics.

What have all these things in common? They don't require AA4 batteries to run. They can be packed in the quite small case.

Sextants are pricey stuff, if you go for a special metalic ones. I am talking abaout a 4-digit number. However Davis Company produces cheaper plastic ones. Here's one for 60 bucks or so. Perfect for training. I didn't have this then, so I used Ship's main sextant. Plotting sheets can be bought or cunstructed for different North and South laitutudes. Chronometer is something an Officer would carry with him, when abandoning the ship for instance. But if you previously corrected your wristwatch against chronometer, you're good to go. Today GPS's report GMT (Better word is UTC) to within a second. Rulers, dividers, and pencils are.. basic instruments on board every ship.. I remember that every deck officer on board had his own set as well in the cabin. Nautical Almanac? You can buy them online. It is pblished jointly  by US Naval Observatory and Her Majesty Nautical Almanac Office. These are pricey too. There's a number of software based almanacs but again, what you need a paper type, to be off-grid reliable.  it's not a hefty price. But on the other hand... Thinking costs nothing. And by doing it, one can only learn new stuff during the process. So I decided to make my own Nautical Almanac. And decided to name it:

Slovenian Nautical Almanac - Slovenski Navtični Almanah

Why Slovenian Nautical Almanac? Well, I don't see this type of publication being published in Slovenia. If it is, I apologize, but it hasn't come to my attention. And being a former Slovenian Merhant Marine member, I feel I have to give back my own little bit to the seafaring comunity in Slovenia. One probably questions why am I writing this in English. Slovenia is a small country, and I don't expect that too many are interested in the subject of marine navigation. And those who keenly are, are probably already in posession of a decent level of knowledge in English language, grammar, and otherwise.  If there will be an interest to rewrite this in Slovenian, I'll try to. But for now, i'll keep it in English.

So come and join me on this mathematical, astronomical, nautical, and programming journey.  I plan some 10 or so posts on the subject. A lot of Mathematics, some programming hints, and some memories from time, when I learned this hands-on. And when a 18-year old boy from Ljubljana stood at the jackstaff on the bow, and... and it was.. magic. 

Best regards.

P.S. I would like to thank mr. William Folkner from NASA Jet Propulsion Lab (JPL) for kindly clarifying licensing terms for using NASA JPL DE Ephemerides data.

P.P.S Gea and Rok. I Love you. Dad