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Fig. 23 shows a cut of 'the earth with the equator dividing it in half. The position of the Great Lakes is The sun is shown crossing the equator and coming north and then going back again. The Great Lakes being north of the equator are always in north latitude but the sun is in north declination only part of the time. She then crosses the equa- tor and goes into south declination. When your ship's latitude is north and the sun's declination is north you look for the azimuth where it' reads "Declination--Same as--Latitude." But when your ship's latitude is north (as it always is onthe. great lakes) and the declination of the sun is south then you look in the book for the azimuth where the head of the page reads "Declination--opposite to-- Latitude." In the foregoing cut we mean that the sun's rays fall directly on the earth at the places and time shown. © The sun, in the heavens, is crossing the Celestial equator at the same time its direct rays are crossing the earthly equator. The Celestial equator is called the Equinoctial. It is very easy to find the declination of the sun for any day in the year. The Hst given below will give you this information or you can get this, and all the other data you need on one of our Pelorus cards: See "Pelorus cards): nese cards are simply all the data we need pasted on a card. We refer to the card when we take bearings--no need to lose much time finding latitude, Standard every- shown. declination, correction for time, : Hquation: of. time, ete, thing is right at hand. Table of Declinations of the Sun. In the Red Book of azimuths bear- ings are given only for heavenly bod- ies that come as far north as declina- tion 23 or as far south as declination 23. In the Henrich book of azimuths bearings of heavenly bodies that come as far north as 29 declination can be taken. Therefore all the stars and planets that we use must ve to the southward of us. However, on ac- count of their great distance from us home stars that we .can use appear to us to be much farther north than they really are. It takes an immense amount of labor to prepare azimuths and for this reason no azimuth book has been published that will give you bearings of stars that are in any part of the heavens. The sun, moon and planets never come farther north than declination 23, so the tables can al- ways be used for them. And so many good stars lie in this belt of azimuths "'TAE Mariné KEVIEW that we have all we need for any pur- pose. We should bearings now be able to take of: the sun. Ino the next chapter we deal with the stars, how to take bearings of moon, stars and planets, how to figure sidereal time from standard time, how to pick out some good stars for use, and how to distinguish stars from planets--al] of which is the most interesting part of the whole work. But we must now try our hand at taking bearings of the sun to see if we have thoroughly mastered it. Some say they would be afraid to put much dependence in bearings of the sun, as there is so much figuring. They say that if one little necessary item is left out a great mistake would be made. But we can overcome this very easily, and in.stich a way that a mistake: is impossible. For this purpose we use what swe call a pelorous slate; It is an old-fashioned school slate with a skeleton of the whole problem scratched into it with some sharp pointed instrument. This prevents the main part of our problem ever being rubbed off. All we have to do each time is to add the necessary figures with a slate pencil. Our pencil marks can easily be rubbed off but the form remains. One side of the slate we will use for taking bearings of the sun and the other side for bearings of the moon, planets and stars. A Pelorous Slate. The cut below shows a pelorus slate with the problem scratched in with' a sharp pointed instrument in such a way that it cannot be rubbed off. The slate is divided into three parts. The first part is for changing your stand- ard time into apparent time. -When we get this apparent time we put it - opposite the word time below. From our Pelorus card we get the latitude of the ship and the declination of the sun and put them in their proper place. We now use these three things to get the true bearing from the Azi- muth book. We put this true bearing in its proper place and then from our pelorus card we get the variation. This changes our true bearing into a magnetic bearing. We then take a bearing of the sun with our instru- ment and we find our error at once. The cut below shows us how our slate looks with the skeleton problem in-- A Pelorus Slate. In the following table we show part of a Pelorous card. On this you will Gnd all the data you need to fill in the above slate. We will then work a problem and fill in the slate. Under scratched 31 the head of "Pelorus cards" we show the complete card that can be used for any place on the lakes, (he eg a |!) I I) fi : Hy Ned. Part of a Pelorus Card. Lati- © Vari- Correction for : tude ation Standard Time 'Cleveland 42 3° west Add 30 min. | Southeast Shoal 42 2° west Add 30 min. Marblehead Pt. 42 1° west Add 29 min. Bar Point We will now take a bearing of the sun, at Cleveland, August 22. Our watch showed the time to be. 9:18 Central Standard time, Remember it is not mecessary t0 do any figuring until after you have taken the bearing with your pelorus. You can then retire to your room and let the ship run while you do the figuring. Or you can do your figuring A GENTRAL STAND HE - ine ON CaIN CNL eee Tact Re iy WRU An ea IX x ANA N Oates ian en | H Your APPARENT LIME 1S | Nid h cate anh te (_ (|| NEN awa aitoh ah COU ae saeco ar : DECUNAT ON OFTHESUN-)2 N OUNS TRUE BEARING Fx. BOOK-- aes THE VARIATION -- Cail HIS GIVES SuNS MAG.2EARING- 129 E HE BEARNG.BY Pecorus --) 36 HE DEVIATION oF COMPASS-- 7 FE iy! |