EXPLANATION OF TABLES 13 
TABLE 41.—CORRECTIONS TO BE APPLIED TO FIND THE TRUE ALTITUDE OF THE 
MOON FROM THE OBSERVED ALTITUDE ABOVE THE HORIZON. 
In this table, which is to be entered with the observed altitude in the side column and from the 
top with the horizontal parallax as obtained from the Nautical Almanac for the time of observation, 
there are set down the corrections to be applied to the observed altitude of the moon’s upper limb 
above the horizon, and also of the lower limb, giving the combined effect of the astronomical 
refraction for the mean state of the atmosphere. and of the parallax and semidiameter of the 
moon. The auxiliary table for height of eye gives the correction for dip. 
TABLE 42.—CONVERSION OF ARC AND TIME. 
This table, which is divided into three parts, contains: First, angular measures of arc from 0° to 
360°, with corresponding values expressed in time (hours and minutes); second, angular measures of 
are from 0/00’’ to 60'00’’ with corresponding values expressed in time (mint tes, seconds) ; third, angu- 
lar measures of are 0’’ to 60’’ with corresponding values expressed in decimals of a second of time. 
The table will be especially convenient in dealing with longitude and hour angle when converting 
from time to arc or vice versa. 
TABLE 43.—CONVERSION OF LOCAL CIVIL TIME TO GREENWICH CIVIL TIME. 
This table is divided into two parts, the upper part is for places in west longitude and the lower 
for east longitude. The table is entered with local civil or watch time of place then under the column 
of longitude or time zone of observer is found the G. C. T. for the local date. If the G. C. T. is 
found where there are italic type in west longitude, then the Greenwich date is one day ahead of the 
local date, or the next day; if the G. C. T. is found in italic type in east longitude, then the Greenwich 
date is one day before the local date. 
Example: Find the approximate G. C. T. and the date corresponding to a watch time of 11 
p. m. on July 1, Long. 136° W. 
Enter table with L. C. T. 23" and under Long. 135°, the G. C. T. is 84, since it is found in italic 
type the date is one day ahead or July 2. 
Example: Find the approximate L. C. T. or watch time of Washington, D.C., when it is 4 a.m. 
watch time July 4, Manila P. I. 
Enter table of East Long. with L. C. T. 45 and under 120° (—8 zone) is found, G. C. T. 205 
in italic type which is G. C. T. 205 July 3. In the first table (west longitude) look under 75° (+5 
zone) for Washington and for G. C. T. 204, then under L. C. T. is found 154, or 3 p. m. July 3. 
Whenever G. C. T. is found in italic type, the date for L. C. T. is changed from the date of the 
known G. C. T.; in other words, it is a reversal of the process. 
