The Star Compass by Nainoa Thompson

The star compass is the basic mental construct for navigation. We have Hawaiian names for the houses of the stars—the place where they come out of the ocean and go back into the ocean. If you can identify the stars as they rise and set, and if you have memorized where they rise and set, you can find your direction.

The star compass also reads the flight path of birds and the direction of waves. It does everything. It is a mental construct to help you memorize what you need to know to navigate.

You cannot look up at the stars and tell where you are. You only know where you are in this kind of navigation by memorizing where you sailed from. That means constant observation. You have to constantly remember your speed, your direction and time. You don’t have a speedometer. You don’t have a compass. You don’t have a watch. It all has to be done in your head. It is easy-in principle-but it’s hard to do.

The memorization process is very difficult. Consider that you have to remember those three things for a month-every time you change course, every time you slow down. This mental construct of the star compass with its Hawaiian names is from Mau. The genius of this construct is that it compacts a lot information and enables you to make decisions based on that information.

How do we tell direction? We use the best clues that we have. We use the sun when it is low down on the horizon. Mau has names for the different widths and the different colors of the sun’s path on the water. When the sun is low, the path is narrow, and as the sun rises the path gets wider and wider. When the sun gets too high you cannot tell where it has risen. You have to use other clues.

Sunrise is the most important part of the day. At sunrise you start to look at the shape of the ocean-the character of the sea. You memorize where the wind is coming from. The wind generates the waves. You analyze the character of the waves. When the sun gets too high, you steer by the waves. And then at sunset you repeat the process. The sun goes down-you look at the shape of the waves. Did the wind direction change? Did the swell pattern change? At night we use the stars. We use about 220, memorizing where they come up, where they go down.

When it gets cloudy and you can’t use the sun or the stars all you can do is rely on the ocean waves. That’s why Mau told me once, “If you can read the ocean you will never be lost.” One of the problems is that when the sky gets black at night under heavy clouds you cannot see the waves. You cannot even see the bow of the canoe. This is where traditional navigators like Mau are so skilled. Lying inside the hull of the canoe, he can feel the different wave patterns as they come to the canoe, and from them tell the canoe’s direction. I can’t do that. I think that’s what he started learning when he was a child with his grandfather, when he was placed in tide pools to feel the ocean.

In 1979, when Mau was confident that I could guide the canoe by myself, he said, “Now I am going to go to sleep; you follow this star path.” And like an overly eager student, I wanted to try sailing in a different direction to experience what the wave patterns felt like when I changed directions. I thought he wouldn’t notice because he was sleeping inside the hull. When morning dawned, he came up and said, “Okay, what course did you sail last night? What star bearing did you hold?” He knew I had changed course. Lying in the hull, he actually knew the course I had steered; he challenged me to tell him in order to make sure that I knew where we had gone.
Tahiti is smaller than Maui and it is a hard target to hit from 2500 miles away. Even hitting a target as large as the Big Island from that distance is outside of the accuracy of our navigation. When we go down to Tahiti, we have a mental image of our course line plotted for the trip. We try to stay on this course and end up in what I call a box. (See the map of the 1980 voyage to Tahiti.) This box is large enough to compensate for any errors in our navigation. In this box there are many islands. All we have to do is to find one of them, and from that island we can find the others. For example, the target when we sail to Tahiti is a box four hundred miles wide, from Manihi in the Tuamotu islands to Maupiti in the leeward Tahitian islands. The first part of the journey to Tahiti is not trying to get to Tahiti but to make sure that we sail into this box and find an island. On different voyages, we have found Matahiva, Tikehau, and Rangiroa-all islands in the box. Since these are coral atolls it is very difficult to tell one from the other, so sometimes we have to land and ask the people what island it is that we’ve found. From any of these islands, we know Tahiti is only about 170-180 miles away and our navigation system is accurate enough to find it from that distance.

Now consider another navigational problem-finding Hawai‘i from Tahiti. The Hawaiian islands are 315 miles wide, from Ni‘ihau to Kumukahi on the Big Island, but if you approach them from the southeast they are a narrow target because they are aligned southeast to northwest. The technique we use is to sail up to the latitude of Hawai‘i on the east side of the islands, using the stars to tell our latitude. When we determine we are at the mid-latitude of Hawai‘i, 20.5 degrees N, we turn west and try to sail into the islands on this side, 240 miles wide-the sight distance from South Point on the Big Island [18.5 degrees N] to the sight distance from Hanalei on Kaua‘i [22.5 degrees N]. Again, our navigation system is accurate enough to hit this target. (See the map of the 1980 voyage to Tahiti.)

The Southern Cross is really important to us in determining latitude. It looks like a kite. The top and bottom stars in the kite always point south-Gacrux on top and Acrux on the bottom. If you are traveling in a canoe and going south, these southern stars are going to appear to be moving higher and higher in the sky. If you went down to the South Pole, these stars are going to be way overhead. If you are sailing from Tahiti north to Hawai‘i, the Southern Cross gets lower and lower the farther north you go. At the latitude of Hawai‘i, the distance from the top star to the bottom star is the same distance from that bottom star to the horizon about 6 degrees. This configuration only occurs at the latitude of Hawai‘i.