Romantically, we sailors love to say that in the night we talk with the stars, they listen to us and respond. We ask them to show us the way to back home, or if they can tell us where we are when the ship is in the nowhere of the immense ocean, other times we simply share thoughts and secrets, homesickness or a love that we cradle in our hearts. The stars always respond, punctually indicating the route to follow. This is a sort of bond almost as old as humanity. The most fascinating thing about astronomical navigation is that fantasy mixes with reality, in a literal sense. Basically on Earth to orient ourselves we use only one system, that of geographical coordinates, using the North and South Pole, the East and West cardinal points, the Equator and the Greenwich Meridian as reference points. With these references, through latitude and longitude we find any position, whether it is ours or that of the destination. With astronomical navigation, however, we can use four systems, two that refer to the observer called “Hourly local coordinate system and Altazimuth local coordinate system”, and two “Uranographic” systems, Equatorial Uranographic and Ecliptic Uranographic. The celestial bodies, whether planets or stars, each have their own distance, their own height, etc. Furthermore, the universe is immense, threedimensionality must be taken into account, and that certain stars have very large distances. With a bit of cunning and pure imagination we invented the “Celestial Sphere”, which when drawn on a plane becomes “a circle around the Earth”, and it is pretended that all the stars rest on this Sphere. By “stretching” the terrestrial references they are expanded to the Celestial Sphere, the North Pole becomes the “North Celestial Pole” (PNc), the South Pole becomes the “South Celestial Pole” (PSc), and the Equator becomes the “Celestial Equator”. The circles parallel to the Equator, on Earth called Parallels, in the Celestial Sphere are called “Parallels of Declination”, the circles parallel to the observer’s horizon are called “Almicantarat”. Exactly as on Earth we orient ourselves with the compass and the North Pole, with astronomical navigation we orient ourselves with the angle at the pole between the star and the reference pole, or with the Zenith which would be the axis that crosses the observer, Zenit at the top and Nadir at its opposite. Just as the Earth’s axis passes through the Earth, an axis passes through the observer using perspective as if he were “the pole”. Today’s astronomical navigation is done by making observations with the sextant, calculations with the formulas of Euler and Neper’s theorems and the data taken from the Nautical Almanac and Nautical Tables, and by tracing the graph of the height lines. In this way we can find our position even when sailing far from the coast in the open sea, and the route to follow. More or less it has always been done like this, considering that Euler lived in 1700 and Neper about a century before him between 1500 and 1600, in ancient times instruments were still used for the detection of the Stars and sufficient knowledge to be able to determine the position of the ship and the route to follow. After the technological boom of the last century, especially in the last twenty years between 1980 and 2000, ships were equipped with so many technological devices (Radar, GPS, AIS, LRT, etc.), that many colleges and nautical schools, even some naval academies have decided to eliminate courses and lessons in astronomical navigation, considering it obsolete and useless. In truth this is not the case, indeed, even today in international conventions all devices and technological equipments are defined as “navigation aids” and are not mandatory, while the compass and log remain mandatory. In short, if a ship in port does not have a GPS, in theory the ship cannot be stopped by the authorities, while if lacks a compass they stop the ship and the captain must take the compass on board to obtain clearance for departure. It must also be considered that geolocation satellites are private or national, they have no obligation to provide the service, and above all they can be deactivated or obscured at any time and for any reason, especially for security reasons. Just an example, if a nation goes to war, feels threatened or has imminent security threats is detected, they can disable or black out its satellites and stop providing service. Considering that today the devices on the bridge are also interfaced, and that therefore the malfunction or deactivation of an instrument also causes problems in the other devices, today astronomical navigation still remains a safety feature for the conduction of the ship. Astronomical navigation is “coming back into fashion”, even the nautical schools and naval academies that had removed it from courses now have readmitted it and are starting to give lessons again. After all, in addition to being beautiful, romantic, ancient in its maritime traditions, it is also a security for all masters who venture out to sea. Even today, two astronomical measurements are made a day on board Italian ships and on the bridge the officers write, often on the chart table, “The stars never lie”.

You never stop learning, that why in my spare time I enjoy scouring the web in search of topics, courses, articles concerning the maritime sector. When I saw the online course, the title immediately caught my attention, because it’s a very special title in the eyes of a seaman. In addition to having a technical-scientific definition, navigation is also defined as "The art of not getting lost". So the title immediately intrigued. I followed the course with great interest, at the end I had some reflections. Actually the course doesn't talk about how we are lost without longitude, the course talks about how problems related to longitude were solved, how it was discovered. The course is well done, it shows with photos and descriptions many ancient instruments used in navigation, to determine the position and find the correct direction to follow (the route). Gives much space to the studies and work done by John Harrison and his clocks. Making a course on any subject in the maritime sector is not very easy. Many things are connected to each other, and each would need its own course. Navigation is closely linked to nature, to ships and their evolution over the centuries, to crews and their knowledge increased. It is almost as old as Humanity, its origins are lost in history, and despite everything some things have not been fully resolved and many things have not been fully discovered. For example, Humanity reached the Moon, but has not yet fully explored the ocean's seabed, or completed the explorations, there are some areas still under exploration, especially in Antarctica. Staying focused on the course, it's clear from the contents themselves that, longitude having been discovered 300 years ago, we have more history of navigation without longitude, than with longitude. To today's seaman, it would seem very difficult imagine to sail without today's knowledge and technology. But a careful analysis would show how navigation hasn't changed that much over time. In fact, between the ancient seamen and those of today, there are still many things in common, such as: They navigate the seas for trade, military purposes, explorations. They face the same uncertainties and risks related to sea conditions, storms and unexpected events. They depend on the knowledge of navigation, and on the equipment and strumentations used to reach their destinations safely and efficiently, not always with a clear sky that allows you to see the stars for orientation, but also with any kind of weather conditions. We tend to underestimate the skills and knowledge of ancient sailors, but there are historical traces that show that they were able to navigate even reaching destinations very distant from their departure's points. Some examples are the invasions of the Sea Peoples in Egypt in the 12th century BC, the Hellenic colonization in the Mediterranean area, the Phoenician civilization, etc. In the world many ancient civilizations have developed remarkable skills in navigation, although much of this occurred as coastal navigation, it was not uncommon to navigate on the open sea (out of sight of the coast). Obviously they didn't have much knowledge that we have today, on geography, astronomy, meteorology, oceanography, etc. But it's clear that they had sufficient notions, knowledge and instruments to be able to navigate and reach even distant destinations. The main factor is that the ancient instrumentation, however rudimentary it was elaborated, but being built with raw materials that are difficult to resist over the centuries, today there are almost none left, and when we refer to ancient instrumentation, really it is the instrumentation used in the Middle Ages, or until a few centuries ago. Rarely some ancient instrumentation have been found, such as the Machine of Antikythera, built in metal and dating back to 100 BC. which is an ancient astrolabe, used for navigation with astronomy, found in the wreck of an ancient roman sunken ship (post’s picture), or historical traces such as the one left by Hipparchus of Nicaea, who in his writings tells us about the astrolabe in the II century BC. Navigation has contributed a lot in the history of humanity, nautical explorations have revolutionized the conception of the world, above all they have colored the maps from the earliest times to today. The historical traces report some important ancient explorations, such as that of Annone the Phoenician, who in the V century B.C. he explored the African continental coasts going far south in the Atlantic Ocean. The explorations of the Greek navigator Pytheas, carried out in 300 BC, describing the British Isles and Iceland in his travels. Until the great medieval explorations with the famous "official" discovery of the American continent in 1492, even if there are historical traces of European civilizations that reached the American continental coasts in more ancient times, such as the Vikings for example. This is why a title like "Lost without Longitude" is very intriguing, being strongly in contrast with the history of navigation, and with the romantic definition of navigation itself. Beyond all, the team of professors has written a very well done course, and I hope they will do others, I will certainly follow them with interest. Thanking you for the time you dedicated to me, I take this opportunity to extend a cordial greeting.