7 E. of Comp. Deviation.. 7 47 W.-Error being to the left of the Variation. 15 E.—True Azimuth being to the right of Observed. THE SAME WORKED BY "BURDWOOD'S TABLES." With Latitude 35° S. and contrary name to Declination, and with 8h 2m Apparent Time at Ship at the side, and 14° 2' Declination on top, take out 124° 10'. EXAMPLE II. (WITH THE MEAN TIME AT GREENWICH GIVEN.) 1885.-August 15th, A.M., Mean Time at Greenwich, 14d 17h 10m os; in Latitude 35° S; Longitude 50° E. The observed altitude of the sun's lower limb 20° 1' 50". Height of eye 17 feet; bearing by compass N.E. N. Variation 15° E. Required the Error of the Compass, also the Deviation. I. The remainder of the work is the same as in last Example. EXAMPLES FOR PRACTICE. 1885.-August 17th. Mean Time at Ship 9h 17m 408 A.M.; in Latitude 2. 1885.-September 23rd, P.M., Mean Time at Greenwich 22d 19h 42m 0s; 3. 1885.-October 4th, Mean Time at Ship 8h 51m A.M.; in Latitude 4. 1885.-November 9th, A.M., Mean Time at Greenwich 9d oh 12m os; 5. 1885-December 14th, Mean Time at Ship 2h 59m 368 P.M.; in Latitude 34° 30' N.; Longitude 60° 14' E. The sun's bearing by compass was West. Observed altitude of the sun's lower limb 17° 21′ 50′′. Height of the eye 18 feet. Required the true azimuth and error of the compass; and supposing the variation to be 30° W., required the deviation of the compass for that position of the ship's head." 6. 1885.-January 28th, A.M., Mean Time at Greenwich 284 3h 55m 188; in Latitude 51° 9' S.; Longitude 109° 23′ W. The sun's bearing by compass was E. by N. Ñ. Observed altitude of the sun's lower limb 36° 8′ 55". Height of the eye 16 feet. Required the true azimuth and error of the compass; and supposing the variation to be 20° W., required the deviation of the compass for that position of the ship's head. 7. 1885.-February 24th, Mean Time at Ship 8h 11m 88 A.M.; in Latitude 38° 2' N.; Longitude 169° 13' W. The sun's bearing by compass was E.S.E. Observed altitude of the sun's lower limb 16° 21' 9". Height of the eye 14 feet. Required the true azimuth and error of the compass; and supposing the variation to be 10° E., required the deviation of the compass for that position of the ship's head. 8. 1885.-March 20th, A.M., Mean Time at Greenwich 19d 22h 30m os; in Latitude 30° 0' S.; Longitude 27° 51' 30" W. The sun's bearing by compass was E. S. Observed altitude of the sun's lower limb 31° 51′ 13′′. Height of the eye 18 feet. Required the true azimuth and error of the compass; and supposing the variation to be 23° 59′W., required the deviation of the compass for that position of the ship's head. 9 1885.-April 12th, Mean Time at Ship 3h 56m 328 P.M.; in Latitude 41° o' N.; Longitude 37° 41' E. The sun's bearing by compass was S. 75° 30' W. Observed altitude of the sun's lower limb 28° 51′ 42′′. Height of the eye 28 feet. Required the true azimuth and error of the compass; and supposing the variation to be 17° E., required the deviation of the compass for that position of the ship's head. 10. 1885.-May 4th, A.M., Mean Time at Greenwich 3d 17h 25m 128; in Latitude 37° 2' S.; Longitude 49° 25′ 45′′ E. The sun's bearing by compass was E.N.E. E. Observed altitude of the sun's lower limb 19° 55' 50". Height of the eye 18 feet. Required the true azimuth and error of the compass; and supposing the variation to be 26° W., required the deviation of the compass for that position of the ship's head. 11. 1885. June 14th, Mean Time at Ship 8h 9m 28 A.M.; in Latitude 60° N.; Longitude 49° 19' W. The sun's bearing by compass was E. N. Observed altitude of the sun's lower limb 35° 49' 15". Height of the eye 16 feet. Required the true azimuth and error of the compass; and supposing the variation to be 10° W., required the deviation of the compass for that position of the ship's head. 12. 1885.-July 7, P.M., Mean Time at Greenwich 6d 13h 42m 368 ;in Latitude 51° 30' S.; Longitude 172° 32′ 30" E. The sun's bearing by compass was N. by E. E. Observed altitude of the sun's lower limb 14° 15′ 20′′. Height of the eye 15 feet. Required the true Azimuth and error of the compass; and supposing the variation to be 20° 59′ W., required the deviation of the compass for that position of the ship's head. REDUCTION TO THE MERIDIAN. TO FIND THE GREENWICH APPARENT TIME. To the time by watch apply its error. If slow add; if fast subtract. Then turn the Run or D. Long. into time. If Run If Run is to the Eastward add; if to the Westward subtract. This gives the apparent time at ship, from which the time from noon must be found.* Turn the Longitude into time and apply it to the apparent time at ship. If East subtract; if West add. The result is the Greenwich apparent time, for which take out the declination from page I. of the month, and correct it in the usual manner. 2. If the time by chronometer is given:— TO FIND THE APPARENT TIME AT SHIP.-To the time by chronometer apply the error. This gives the mean time at Greenwich, for which time take out the declination and equation of time from page II. of the month, correcting each in the usual manner. To the mean time at Greenwich apply the equation of time, as directed on page II. of the month. The result is the apparent time at Greenwich, to which apply the longitude in time. If W. Long. subtract; if E. Long. add. This will give the apparent time at ship or time from noon. If more than 12 hours subtract from 24 hours for time from noon. * TO FIND THE TIME FROM NOON.-If A.M. at ship, subtract the apparent time at ship from 24h; but if P.M. at ship, the apparent time at ship is the time from noon. TO FIND THE TRUE ALTITUDE.-Proceed as in previous problems. Seek the sum of these Logs. in Norie's, at page 104, &c.. Table XXV., where it can be taken out to the nearest ten seconds. This gives half the reduction, multiply it by 2. This is the reduction, which must always be added to the true altitude. The result is the true meridian altitude To find the LATITUDE.-Subtract the true meridian altitude from 90°, the remainder is the meridian zenith distance, which must be named of an opposite name to the bearing. That is: If bearing is North, the zenith distance is S.; If bearing is South, the zenith distance is N. Below the zenith distance place the corrected declination. The result is the latitude, of the same name as the greater of the Z. dist. and declination. Note -When taking out the Log. of time from noon from Table XXXI., if the Index in the Table is or it means that in the line of Logs. to the right, the Index changes from 5 into 6, or from 6 into 7. It changes when the first figure in the Log. changes from 9 to 0. The same remarks also apply if Log. rising is used for this problem. |