Speculum nauticum a looking glasse for sea-men : wherein they may behold a small instrument called the plain scale whereby all questions nautical and propositions astronomical are very easily and demonstratively wrought ... / by Iohn Aspley.

CHAP. XVIII

The elevation of the Pole, and declination of the Sun, given to finde the difference of the ascentions.

The Poles elevation is 51 degrees 32 minutes, the de∣clination of the Sun is 21 degrees.

[illustration]

dem: 13:

FIrst draw the Line B A K, re∣presenting the Horizon, then upon the Centre A, draw the Circle B C D E F, Then from K, unto D, set the elevation of the Pole which is 51 degrees, and 32 minutes: then from the point D, by the Centre A, draw the line D A F, representing the Pole of the world:

then from R, unto C, set the complement of the Poles elevation which is 38 degrees, and 26 minutes, then from C, by the Centre A, draw the line C A E, representing the Equinoctiall Line; then from C, un∣to G, and likewise from E, unto H, for the declinati∣on of the Sun, which is 21 degrees, then from G, un∣to H, draw the parallell of the Suns declination, cut∣ting the Pole of the World in L, and the Horizon in I, then set one foot of your compasses in the point L, and extend the other unto G, then with that distance of your Compasses draw the Semicircle G M N H, then opening your Compasses unto the radius of your Scale, and upon the same centre draw a Concentrick circle, G X O H, then from I, where the declnation of the Sun doth cut the Horizon, draw the line I N, parallell unto the Pole of the World A M, cutting the circle G M H, in N, then lay your Ruler from the point I, unto the point N, and so draw the line N O, cutting the Concentrick circle G X O H, in O, so shall the distance of O, and X, be the difference of the ascentions, which is here found to be 28 degrees, and 54 minutes.