. Tables of calculated hour-angles and altitude azimuth table 30N. to 30S. : ex-meridian tables 60N. to 60S. and calculated reductions ans azimuths of bright stars from 1 hour to 3 hours from Meridian / c by Blackburne . Y THE MARCQ ST HILAIRE SYSTEM OLD SUMNER METHOD 1ST Observation. 2ND Observation. A. Lat. i8 o N. gives Long. 70 7-6 E. B. ,, 18 40 ,, „ 70 0-7 E. Gives Long. C. 71 25-7 E. Run in interval.„ „ D. 70 13-7 E. N. 77° E. 56 m. Resultant Position plotted on the Chart at 2nd Observation : Lat. 18° 11 N., Long. 71 6 E. MARCQ St HILAIRE SYSTEM 1ST Posn. Lat. 18 o
. Tables of calculated hour-angles and altitude azimuth table 30N. to 30S. : ex-meridian tables 60N. to 60S. and calculated reductions ans azimuths of bright stars from 1 hour to 3 hours from Meridian / c by Blackburne . Y THE MARCQ ST HILAIRE SYSTEM OLD SUMNER METHOD 1ST Observation. 2ND Observation. A. Lat. i8 o N. gives Long. 70 7-6 E. B. ,, 18 40 ,, „ 70 0-7 E. Gives Long. C. 71 25-7 E. Run in interval.„ „ D. 70 13-7 E. N. 77° E. 56 m. Resultant Position plotted on the Chart at 2nd Observation : Lat. 18° 11 N., Long. 71 6 E. MARCQ St HILAIRE SYSTEM 1ST Posn. Lat. 18 o N., Long. 69 30 E. H. M. s. 15 7 30 T. Alt Long. E. +4 38 o Run Cor. 30 12-0+ 0 55-9 Sp. 19 45 30 Alt. at 2nd Obsn. at2ndObsn. Gives cal. 0 31 7-990 00 4 14 30 58 52-160 23-3 I 31-2 = at 2nd Obsn.: Lat. 18 13 N., Long. 7028 M. s. o / 19 20 16 True Alt. 88 loj Long. E. +4 41 52 I 49i o 2 8W. Gives cal. i 27 Away from (t) o 22J Azimuths. i6J°W. Azimuth N. 8oJ° E. Resultant Position plotted on the ChartTrue Position ..... Lat. 18 28 N., Long. 71 2-5 18 20-3 N., Long. 71 3-7 E. Poiby flafcq St Hi/oire Systemfoi by Improved Sumner rieltioi. f^ote.—The St Hilaire system would have given the same accuracy as by the Improved Sumner Methodif the problem were worked by the method shown by Brent in his ex-meridian book (combining chronometerobservation and the St Hilaire method), and no chart is needed ; or an accurate result would also be obtainedif the first observation had been plotted on the chart before the second observation was taken, and theapproximate longitude from this position-line had been used in obtaining the hour-angle and azimuth forsecond observation. The plotting on the chart, in a somewhat extreme case, has been here given to clearly Hlustrate thepossible errors which may arise from following the plan as given above, and advocated by some recentauthors. Although one of these authors,
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