The increased speed of aircraft and surface vessels has had a decided influence on navigation methods during the past fifteen to twenty years. Spurred on by the new demands our highest authorities on navigation have developed tables and methods which reduce to a minimum the time required to solve for the line of position of a celestial body.
One of the results of these combined efforts is a growing tendency to favor the use of the Greenwich hour angle methods of solution which are more easily solved. It has been pointed out that it is quite practical to give the Greenwich hour angle directly in the Nautical Almanac thus eliminating the steps now necessary to apply the equation of time in the case of the sun or right ascension values in the case of the moon, planets, and stars. In accordance with this movement the 1932 Nautical Almanac lists the Greenwich hour angle of the moon for each hour. Evidence that the same step relative to sun, planets, and stars is being considered at this time is shown by certain of the questions contained in a Hydrographic Office questionnaire now being circulated among those interested in navigation.
The purpose of this paper is not to dwell on the relative merits of the various methods advanced. The writer acknowledges with thanks the fine work resulting in the shorter and easier methods which has been done by the pioneers in this study. While discussing these shorter methods with Lieutenant C. D. Williams, commanding officer of the U.S.N.R. Aviabase at Grosse Isle, it occurred to us that no publication has been made to date of the advantages which might be gained by collecting all requisite data for one day sheet in the Nautical Almanac. It be noted that the same number of stars are given as appear in H.O. 209, plus Polaris.
To bring out the advantages of such an arrangement an analogy might be drawn with the daily weather map. Here, on one sheet is found all of the information for Mr. American to comprehend what is going on as far as weather is concerned throughout the country. Imagine the storm of protest which would go up if these same individuals were now asked to wade through a volume listing the data for the whole year if the same could be possible. And yet navigators for centuries have been asked to do the same thing as regards the celestial bodies when they set out to plan their day’s work with the use of the Nautical Almanac, although it is only one day which they are interested in for the time being.
Many interesting things are apparent at a glance from an almanac arranged as suggested. Can I take a sight of Venus or the moon for a fix with the sun during my cross-water hop today? What stars will be visible at evening twilight? All is easily answered when the new form is perused. Knowing the Greenwich hour angle for the sun for the Greenwich civil time under consideration, all other bodies may be quickly oriented by the application of their Greenwich hour angles all worked out before you.
To be sure, the publication of data in this way will result in a larger volume of printing. To keep down the size of the book necessary to be carried at any one time the almanac could be printed for six months, three months, or even in daily sheets. The latter should be popular with the aviator who can tuck a couple of sheets in his H.O. 208 and feel that he has all the information necessary to make use of the celestial bodies in his flight.
In conclusion the writer again wishes to state that no originality is claimed for the suggestions presented in this article. However, if this suggested arrangement will help to dispel the mystery surrounding celestial navigation or add one iota to the safety of ships of the air or sea by eliminating unnecessary entry into tables, its mission will be accomplished. Possible errors in properly making such entry will thus be transferred from the vibrating cockpit or pitching bridge to the quiet atmosphere of a bureau office where there is time to check and recheck.