EXAMPLE I. (WITH TIME BY WATCH AND RUN GIVEN.) 1885.-July 26th, A.M. at ship. Lat. by account 48° 49' N., Long. 25° W. The observed altitude of the sun's lower limb South of the observer 60° 2 ́50"; height of eye 18 feet, time by watch 26d 9h 14m 20s which had been found to be 9h 33m 588 fast on apparent time at ship. The difference of Longitude made to the Westward was 17' after the error on apparent time at ship had been determined. Required the Latitude by the Reduction to the Meridian. EXAMPLE II. (WITH CHRONOMETER TIME AND ERROR GIVEN.) 1885.-July 26th, A.M., at ship. Latitude by account 48° 49' N.; Longitude 25 W. The observed altitude of the sun's lower limb south of the observer was 60° 2' 50". Height of eye 18 feet. Time by chronometer 26d 1h 51m 188 which was 25m 50s fast on mean time at Greenwich. Required the latitude by the reduction to the meridian. d. h. m. s. Chrn. Time.. July 26 1 51 18 Dec. July 26th 19° 21′ 39′′ N. H. diff. 33.45 -25 50 47 G.M.T. 1.4 -6 14 Long. in Time .. -I 40 The remainder of the work to find the reduction is the same as in the last example. EXAMPLES FOR PRACTICE. 1. 1885. May 21st, A.M., at Ship; Latitude by account 5° 10' S.; Longitude 121° E. The observed altitude of the sun's lower limb North of the observer was 64° 7′ 39′′. Height of eye 20 feet. Time by watch 21d 8h 42m 30s which had been found to be 9h fast of apparent time at ship. The difference of longitude made to the Eastward was 20' after the error on apparent time at ship was determined. Required the latitude by the reduction to the meridian. 2. 1885.—June 28th, P.M., at Ship; Latitude by account 51° 30′ N.; Longitude 152° 10' W. The observed altitude of the sun's lower limb South of the observer was 61° 1′ 40′′. Height of eye 19 feet Time by chronometer 28d 10h 22m 30s which had been found to be 17m 41s slow of mean time at Greenwich. Required the latitude by the reduction to the meridian. 3. 1885.--August 2nd, P.M., at Ship; Latitude by account 20° 10′ S.; Longitude 126° 50' E. The observed altitude of the sun's lower limb North of the observer was 51° 35′ 0′′. Height of eye 24 feet. Time by watch August 1d 23h 17m 408 which had been found to be Ih slow of apparent time at ship. The difference of Longitude made to the Eastward was 26' after the error on apparent time at ship was determined. Required the latitude by the reduction to the meridian. 4. 1885.-September 22nd, P.M., at Ship; Latitude by account 37° 45′ S; Longitude 116° 5' W. The observed altitude of the sun's lower limb North of the observer was 51° 42′ 50′′. Height of eye 20 feet. Time by chronometer 22d 7h 29m 128 which had been found to be 29m 108 slow of mean time at Greenwich. Required the latitude by the reduction to the meridian. 5. 1885.-October 16th, A.M., at Ship; Latitude by account 47° 25′ N; Longitude 15° W. The observed altitude of the sun's lower limb South of the observer was 33° 13' 0". Height of eye 16 feet. Time by watch 15d 21h 2m 388 which had been found to be 2h 39m 108 slow of apparent time at Ship. The difference of longitude made to the Westward was 15' after the error on apparent time at Ship was determined. Required the latitude by the reduction to the meridian. 6. 1885.-November 20th, A.M., at Ship; Latitude by account 56° 30' S ; Longitude 139° 45′ W. The observed altitude of the sun's lower limb North of the observer was 52° 56' 30". Height of eye 20 feet. Time by chronometer 20d 8h 48m 13s which had been found to be 6m 29s fast of mean time at Greenwich. Required the latitude by the reduction to the meridian. 7. 1885.—December 22nd, P.M., at Ship; Latitude by account 49° 16′ N.; Longitude 51° E. The observed altitude of the sun's lower limb South of the observer was 16° 44' 30". Height of eye 19 feet. Time by watch 219 22h 17m 218 which had been found to be 2h 17m 50s slow of apparent time at Ship. The difference of longitude made to the Westward was 27' after the error of apparent time at ship was determined. Required the latitude by the reduction to the meridian. 8. 1885. December 24th, P.M., at Ship; Latitude by account 59° 40′ S.; Longitude 148° 54′ W. The observed altitude of the sun's lower limb North of the observer was 53° 20′ 30′′. Height of eye 19 feet. Time by chronometer 24d 10h 34m 20s which had been found to be 17m 158 fast of mean time at Greenwich. Required the latitude by the reduction to the meridian, 9. 1885.-March 1st, P.M., at Ship; Latitude by account 30° 50' N.; Longitude 100° W. The observed altitude of the sun's lower limb South of the observer was 51° 18′ 32". Height of eye 19 feet. Time by watch February 28d 21h 18m 59s which had been found to be 3him Os slow of apparent time at ship. The difference of longitude made to the Eastward was 37' after the error on apparent time at ship was deter mined. Required the latitude by the reduction to the meridian. 10. 1885.-January 26th, A.M., at Ship; Latitude by account 43° 20′ S.; Longitude 171° 10' W. The observed altitude of the sun's lower limb North of the observer was 64° 23′ 18′′. Height of eye 20 feet. Time by chronometer 26d 10h 58m 25s which had been found to be 14m 29s slow of mean time at Greenwich. Required the latitude by the reduction to the meridian. 11. 1885.-April 19th, P.M., at Ship; Latitude by account 40° 50′ N.; Longitude 91° 10' E. The observed altitude of the sun's lower limb South of the observer was 59° 20′ 4′′. Height of eye 21 feet. Time by watch 19d oh 15m 30s which had been found to be 20m10s slow of apparent time at ship. The difference of longitude made to the Westward was 39' after the error on apparent time at ship was determined. Required the latitude by the reduction to the meridian. 12. 1885.-March 20th, P.M., at Ship; Latitude by account 58° o' S.; Longitude 119° 30′ E. The observed altitude of the sun's lower limb North of the observer was 31° 50′ 50′′. Height of eye 16 feet. Time by chronometer 19d 17h om 378 which had been found to be 36m 29s fast of mean time at Greenwich. Required the latitude by the reduction to the meridian. TO FIND THE LATITUDE BY THE MERIDIAN ALTITUDE OF A STAR. TO FIND THE TRUE ALTITUDE.-Correct the altitude for index error (if any), for dip and for refraction. The result is the true altitude. Note.-No semidiameter, no parallax. TO FIND THE ZENITH DISTANCE.-Subtract the true altitude from 90°, the remainder is the zenith distance. To be named S. if the bearing is N. To be named N. if the bearing is S. TO FIND THE STAR'S DECLINATION.-Open Norie's Navigation, page 76, Table XIII., and find the star's name, note the hour of the right ascension. Then enter the Nautical Almanac at the Table of Fixed Stars, page 318, for 1885, turn forward until you find the right ascension, and close by you will see the star's name; below the star's name is the declination, the degrees and minutes being on the top of the page, and the seconds lower down opposite the day of the month. Note. If the seconds exceed 60 take off 60, and increase the minutes by I. TO FIND THE LATITUDE.-Below the zenith distance place the declination. Then— If Z. dist. and dec., are of same name, add; If Z. dist. and dec. are of different names, subtract. The sum or the remainder is the latitude, to be named the same name as the greater. EXAMPLE. 1885, May 26th. The observed meridian altitude of the star Sirius bearing South 58° 5' 20"; height of eye 20 feet. Required the Latitude. Note. No semidiameter and no parallax required to obtain the true altitude. The right ascension of Sirius is found on page 76, Norie's Tables, to be 6h, &c.; enter the Nautical Almanac page 318, turn forward to 6 hrs. R.A., and on page 331 the star's name, with declination, is found. |