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in hours, minutes and seconds, in- stead of degrees. Now remember that we are figuring on the understanding that the dome of the .heavens turns over our heads every day. ens really stand still while the earth does the whirling. You can now understand that this heavenly first meridian, or the first hour-circle, swings over our heads every day. We will imagine that we can see this immense line pass over our heads. When it is: directly over our heads we will take the time, by our watch. Then, as this great merid- ian swings past we will watch a star coming from the east, towards us. When it gets directly over our heads we will again look at our watch. The length of time since the first hour-circle has passea will then be - this star's right ascension. The right 'ascension of any heavenly body is then its distance, in time, from the first hour-circle, or the first point of Aries. Sidereal time is set by the first point ©f Aries, is directly over your head the sidereal clock should read 0 hours, 0 minutes, 0 seconds. How easy it then is to figure the right ascension of a star. Now please remember that while we are learning just how heavenly bodies are located in the heavens we don't have to locate any of them ourselves. The Nautical Almanac does all this for us and really makes the study very easy after all. Now paint a few stars on the inside of the outer globe in your model and MARCH 2/ But, of course, the heav- When this point ' 'TAe Marine ReEvIEw study them closely. You. can see that the stars will not change their position at all. When the outer globe turns and takes the: hour-circle with it it also takes the stars with it. Their right ascension and declina- tion will always remain the same. (A very slight movement of the stars is caused by the precession of the equinoxes, explained farther on in this work.) But the sun, moon and planets will always be changing the positions. The earth and the other planets are continually rushing around the sun and this makes them all appear to wander in every direc- tion among the stars, Fig. 37 shows the sun crossing the line on "March Zl) Im other words, the sun is crossing the heavenly equa- tor. The exact spot where the sun crosses is 'called the First Point: of Aries. The first heavenly meridian cuts through here as shown in Fig. 38. THE FIRST POINT OF ARIES Ge Fic. 38. & This crossing point has_ several names--the First Point of Aries, the Vernal Equinox, the Spring Equinox, the Greenwich of the Sky, etc. Sev- eral thousand years ago, when astron- omers first laid out the plan of heav- enly latitude and longitude, the sun crossed the line in the constellation Aries. The exact place of crossing was therefore called the First Point of _ Aries. "Precession of . the Equinoxes' the sun now crosses the line in the con- stellation Pisces. But the first name-- The First Point -of Aries--still re- mains. All about the Precession of the Equinoxes, etc., will be found farther along in this work. How to Pick Out the Brightest Stars. If the weather is clear nearly 3,000 : stars can be seen at once with the naked eye. As we see only half of the dome of the heavens at once there must be nearly 6,000 stars in the ae heavens that can be seen without the use of a telescope, But an astronomer can find about 100,000,000 stars with his telescope. For azimuth work we need only about one dozen of the brightest stars, For the purposes of identification the stars are grouped together and each group is called a constellation. Most of the constellations were named by ancient astronomers and very few of them look like the things they were named after. Constellations are generally given Latin names and each star in a con- stellation is designated by a Greek letter. But for the purpose of clear- ness we will designate each star by an English letter as they resemble Greek letters somewhat. Constellations are given such names as Taurus, Aries, Gemini, Cancer, Leo, etc. The English names of these constellations would be The Bull, The Ram, Ihe. Twins, The Grab. ane The Lion. When you are star-gazing don't try to find anything that. re- sembles any of these. The ancient astronomers must have had great im- aginations, In the constellation Taurus we see seven. stars. The brightest star, is named -Faurus <A, then . Taurus Go Taurus C, etc. Generally, however, the brightest star in each constella- tion has a proper name attached to it, The brightest star in Taurus 35 named Aldeberan. It would, there- fore, have two names--Aldeberan, or Taurus A, If it were possible for us to see the imaginary boundary lines that the astronomers have drawn in the heav- ens, to separate the constellations, the sky would look like a map of a state or county. Fig. 39 shows the But on account of the. _ | AURIGA * *PERSEU 3S + if = * ¥ 3 i x cs TAURUS - ht * > ARIES * * * x, | * . ORION 4 Py + x a* . * wg ETUS . * " Kt KR Re * k te . \ og * * -RIDANUS x + * * oe * LEPUS % * COLUMBIA + + Fic, 39.