M. Blundevile his exercises containing sixe treatises, the titles wherof are set down in the next printed page: which treatises are verie necessarie to be read and learned of all yoong gentlemen that haue not bene exercised in such disciplines, and yet are desirous to haue knowledge as well in cosmographie, astronomie, and geographie, as also in the arte of navigation ... To the furtherance of which arte of navigation, the said M. Blundevile speciallie wrote the said treatises and of meere good will doth dedicate the same to all the young gentlemen of this realme.

How to take the altitude of the Sunne, or of any starre. Proposition. 3.

TO take the altitude in any time of the day when the Sunne shineth, you must turne your face and also the left Tablet or Pinule of the Diop∣ter towards the Sunne, holding the Astrolabe by the ring with your right forefinger or middle fin¦ger being the somewhat bowed, in such sort as the A∣strolabe may hang plumbe, and then with your left hand lift the Diopter vp and downe vntill the Sun with his beame due iustlie stréeke through both the holes of each Pinule of the Diopter, so as you may sée the shadow of the two holes of the vpper Pinule to play vpon the two holes of the nether Pinule, then marke vp∣on what degrée of altitude the thinnest edge or fiduciall line of the Diopter falleth in the outermost skirt or border of the backe of the Astrolabe, for that is the Sunnes altitude for that present. But if the Sun be couered with a cloud, so as it shineth not cleare mough to cast any shadow, and yet so as it may be séene with the eie, then hang the Astrolabe by the ring vpon your right thomb, and turning your face towards the Sun▪ lift vp your hand with the Astrolabe so high, as by moouing the Diopter with your left hande vp and downe, you may with your right eie (the other béeing shut) sée the Sunne through the greater holes of both the Pinules of the Diopter, and marke vppon what degrée

of altitude the vpper ende of the Diopter falleth, and that is the altitude of the sunne at the time, and in this maner you must also take in the night season, the altitude of any starre.