The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

star's right ascension. If the latter is the smaller, add 24 hours to-it. The re- mainder will be the time of the star's meridian passage. If you use Page II of Nautical Almanac for the right ascension of mean sun (last column) the remaind- er will be mean time; but if Page I (al- ways the left hand page) the remainder will be apparent time, and to get it into mean time the equation of time (taken from the same page) will have to be ap- plied-to it. Use, Page II. for the day of the month your observation falls on. It is always the right hand page. Example: In 1903 Polaris had a right ascension of 1h 23m 50s (in 1906 it is th 25m 88), and on Dec. 1, 1903, the right ascension of mean sun for Greenwich noon was 16h 36m 4os. The R. A. (ab- breviation for right ascension) of Polaris being less than the sun's R. A., we in- crease it by 24 hrs., equals 25h. 23m. 50s. and 16h. 36m. 40s. subtracted from it equals 8h, 47m. 10s. mean time. To know which star will cross the meridian after a certain hour we have only to invert the above rule, or thus: Add that hour to the sun's right ascen- sion. The sun will be the R. A. of your own meridian. If it is more than 24 hours, subtract 24 hours from it. The star table will then show you what star's right ascension is equal to or a little greater than your own. 'That will be the next star to cross your meridian. If -you are sailing to the eastward it will cross a little ahead of time; if you are going west, it will be a little behind. Ex- ample: Mean time at ship 8h.. 47m. p. m., sun's R. A.for above date and year, 16h. 36m. 4os.; the two added give a sum of 25h. 23m. 40s.; 24h> subtracted from it 'equals the R. A. of Polaris.:: Ii we did not know the R. A. of Polaris and looked into the star tables for a star with a R. A. of th. 23m. 4os. we would find that it belonged to Polaris. We have used Polaris merely for an example, but you can do the same thing with any other star. Bear in mind that here on the Lakes where we employ standard time that we must reduce it to its cor- responding mean time before these ex- amples will agree. You will know whether the star is north or south of you by its declination. If you are in north latitude, the star will be south of you if its declination is north and less than your latitude. If its, decli- nation and your latitude are both north, | and the former is the greater, the star . will be north of you. The same principle applies if you are in south latitude. A star with a declination equal to your own latitude and of the same name, will be directly 'overhead or in the zenith, when it is on your meridian. In our lati- tude Capella is such a star, it having a } 'TTAE Marine. REVIEW declination of nearly 46° north. There are many stars that have practically the same right ascensions, therefore they come to the meridian along about the same time. Their declinations are, in most cases, widely different, and even opposite in name, hence, some will be low down in the horizon and others high up when they pass the meridian; some of them will bear north from you, others south. You can very easily tell when a j! subtract the latitude of your position, or the position used, from 90°. The re- mainder is called co-latitude, and mark it N. or S. the same as the name of the latitude. Then if the co-latitude and dec- lination are of the same name add them; if of different names, subtract. The re- sult is the approximate meridian height of the celestial body in question. The above example worked out according to this rule would be as follows: star is approaching the meridj : Declination of Celestial: Pole. is, 0.4 90° beatin ee g the meridian by its Latittidé of placésiio3 5 cn " 62° N solely as a general reference the fol. papain of Dale 62° N lowing stars of the Big Dipper have the ce ee following R. A's. and Declinations: ey ae at Paes nee me 90° Dibie eae Dé. 62. 16' N. R. A; toh. 58m. as ISDS Nae iae Dec ve 14' N. R. A: 1th, 49m. ZAG yo Dec 5a. N. R, A. 13h, 25m Benetnasch ..... Dec. 49° 48' N. R. A. 13h, 44m, Since Dubhe has a Dec. of about 62°, its polar distance is therefore 28°; in other. words, this star appears to revolve around the true north pole of the heav- ens with a radius of 28° (of declination "Worth. Star <a. Correct Tagnetic Bearing _ Troe Mericiarz Pde Star at Bearing of North Duluth by Variation Com- pass, or a Compass With- out Deviation, -- or celestial latitude). This is equal to At Escanaba, Mich. No Var- jation. saying that Dubhe's orbit or revolution is 28°. For a spectator situated on the parallel of 62° north, would have Dubhe in his zenith when it revolved to his meridian; in other words, if it were pos- sible for this spectator to take no part in the earth's rotation, from that time, but could suspend himself in the air, he would have Dubhe in his zenith con- stantly. , To calculate the meridian height (alti- tude) of a star (or any celestial body) Trve Meridian Note.--Its meridian height when on the meridian below the pole under the above conditions would equal the diam- eter of its orbit minus its height above the pole, or thus: - Radius: of . Dubhe : : ' : 9 9 : £ { \ ' \ wl 4! us a %, Te - ~ x uv \ \ s ey eK w \ Bearing of North Star at Buffalo--Var. Compass. equals 28°, therefore diameter is twice radius 28° or 56°,.and 90° -- 60° = 34°5, its height when on the meridian below the pole. Hence, to calculate the meridian height below the pole, first calculate its height for above the pole and from it sub- tract the diameter of its orbit of revolution around the pole. By subtracting the - polar distance from the latitude gives the same thing, thus: Lat. 62°; polar dis- tance 28°: 62° -- 28° = 34°. Polar dis- tance is the distance in degrees of dec- lination that a celestial body is from the