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28 THE Marine REVIEW Modern Methods of Lake Navigation for the There are many valuable pointers about taking bearings of the sun, moon and stars that can be learned -by practice only, but the following hints may be useful: The nearer the heavenly body is to abeam the better job you can make of it. Don't take a bearing if the object is higher up than 60 degrees. Ke- member that it is 90 degrees from the horizon to the zenith. The zenith 'is the point that is directly over your head. : Therefore don't take bearings of the sun between 10. a. m:.and.2 p, m. unless it is not possible for you to get them at any other time. 'You might be told that refraction and dip of the horizon make heavenly bodies appear in a _ different place than they really are. Don't bother your head about these puzzlers unless you are intending to be an ocean nav- igator... You might learn all these things as a side line after you have mastered that which is really neces- sary, but you had better forget many -- -of. the puzzling terms that you, read of in navigation books and first spend -your time making yourself an expert lake navigator. If we filled our heads with such things as amplitudes, co- latitudes and polar-distances we would be very apt to shy at the whole study. These things can be looked into later on if we wish. The last chapter of this book is devoted to definitions of all such things. We are also told that the moon should not be used for azimuth work --they say it is too close and "its parallax is too great. We are told Beginner. BY CAPT, GEORGE TRIMBLE. ~_ 4, <¥ -- | by « | (eae = #2 -=06 =------W gprowoiat. § = WE ie -- Se y ie \ Zz igs il \\ G ss) Sy oe Ss oO i Se FIG. 28. that it moves too fast through the heavens. It is only 238,000 miles from the earth--that's all. The best lake navigators use the moon. But our books on navigation mean all right--but they are addressed to Ocean navigators. The moon is not reliable for finding the position of a ship on the ocean. Lake navigators often take bearings (or azimuths) of objects that are only a few miles away. A friend of mine--Captain W. E, Clarke, an excellent lake naviga- tor--taught me to find the error of my compass from the reflection of the lights at the Lorain furnace. This is often seen at Southeast shoal. When directly abreast the lightship the azimuth is 149E. Swing your ship on the course you wish to take before you get tothe take lightship and your bearing' when 'éxactly abréast. Do' it quickly as the "angle soon changes, Swinging Ship for Deviation. One of the things that a careful lake mavigator does is to frequently swing his ship for deviation, This is especially valuable when you first leave the dock in the spring. For example, we will say that we have just left Milwaukee with a steamer that has lain at the dock all winter. No figuring need be done until after you have taken all the bearings and have shaped your course down the lake. We first swing our ship to north and steady her there. Make our pelorous read the same and then take a bearing of the sun, moon of a star and note the time. Swing your ship slowly on a port wheel and stop her on each inter-cardinal point as shown in the above cut. Take a bearing and the time at each stop and mark it down. When you have completed the whole circle. shape your course down the lake and figure your deviation out at your =Jeisure. The whole operation will .take butia . _ few minutes and shows you.-the devia- tion of your compass.on every head- "ings the pelorous slate there is not the least chance for mis- take in your problems and you can be By using just as certain of the result as if you