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Maryland Geological Survey, Volume 1, 1897
Volume 423, Page 528   View pdf image (33K)
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528 FIRST REPORT UPON MAGNETIC WORK

Examples of Application of foregoing Tables.

1. Required the Hour Angle and Azimuth of Polaris, at Linden,
Montgomery County, on June 10, 1897, at 8h. 33m. 12s. p. m., accord-
ing to pocket watch keeping standard time.

Geographical position of Linden : Lat. 39.0°, Long. 77.05° W.


h. m. s.


Watch time of observation, 1897, June 10 ..........

... 8 33 12 p.


m. s.



Watch fast on standard time, Im. — 1 00



Reduction of standard time to Linden

-9 12


local mean time = 4 (75-77.05) = 8.2 m. — 8 12



Linden local mean time of observation, 1897, June K

3 .. 8 24 00 p.

h. m.

Astronomical time of " " " "


8 24.0

Astron. time, U. C. Polaris, June 1, 1897 (Table XV)

... 20 35.0


Reduction to June 9' (p. 514) ......................

— 31.5



20 04.1


Check: Astron. time U. C. Polaris, June 15, 1S97.......

19 40.7


Reduction to June 9 or 6 days .....................

+ 23.6



20 04.3


Hence astrou. time U. C. Polaris, June fi, 1897

.... 20 04.2,

subtract2 20 04.2

Hour angle of Polarix, at observation ...............


....... 12 19.8

Subtract f rom .....................................


....... 23 50.1

Time argument for Table X VII ......................


....... 11 36.3

Azimuth of Polaris, at observation ...................


.........0° 08.5' E.

To obtain the meridian lay off 0° 08...V to the west.



2. Required the Hour Angle and Azimuth of Polaris, for Easton,
Talbot County, at 6h. 20.4m. a. m., standard time, November 20, 1900.

Geographical Position of Easton: Lat. 38°.8. Lone:. 76°.1 W.


h. m.


Standard time of observation, Nov. 20 ..............

........6 20.4a


Reduction of standard time to Easton local mean



time — 4(75 — 76.1) — 4.4 m.....................

........ —4.4


Easton local mean time of observation, Nov. 20..........

.........6 16. Oa

h. m.

Astronomical time of observation 1900, Nov. 19......


18 16.0


h. m.


Astron. time U. C. Polaris, 1897, Nov. 15 (Table XV)

.........9 40.4


Reduction to 1900, Nov. 15 .....+4.3 m.

-11.5


Reduction to 1900, Nov., 19.......—15.8 m.



Astronomical time U. C. Polaris, 1900, Nov. 19 ......

.........9 28.9

9 28.9

Hour Angle of Polaris, at observation and Time Arg.,

for table XVII ...

... 8 47. 1

Azimuth of Polaris, at observation (Table XVII)


... 1 09.5 W.

To obtain the median lay off 1° 09. y to the cast.



1 By reference to table XV, the surveyor will observe that the times between June
1 and 15 are greater than 8 h. 24 m. ; consequently, the culmination for one day
earlier, June 9, will be used; see directions p. 524 (bottom).

2 To subtract, take one day from June 10 and add its equivalent, 24 h. to 8 h. 24 m.,
making June 9, 32 h. 24 m. (which is the time expressed by June 10, 8 h. 24 m.);
then subtract in the usual manner.


 

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Maryland Geological Survey, Volume 1, 1897
Volume 423, Page 528   View pdf image (33K)
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