Astronomia Magnetica

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Magnetic Net

The fisherman of fishes, the industrious bird-catcher, the astronomer snatches the fixed stars with his nets

The numbers from the points DC on both sides, both towards A and B, the maximum declination of the Sun, namely 23 degrees and 30 minutes. and by the end, draw straight lines parallel to the Equator, the line of which IS, 69. PN verò W refers to the Tropic; of the other true signs, the parallels and the table of the declination of the points of the ecliptic, or you describe the signs, counting the degree of declination of each sign from points C, & D towards A, & B: for having led through the degrees of declination of each sign competent to parallel lines, you will have the question, as appears in the fourth figure . Inscribe the hourly lines in this way. In the semicircles ACB and ADB, the first rule is placed above the pole A, and each ten or fifteen degrees. equally from point C towards B, or from point D towards Bequali, and distant by the hourly space, see where the rule touches the equinoctial line CDA, and make points there; therefore finding the whole hours by means of points; in no other way will you find the points of the middle hours, and the quarter. For through these points if the two poles A, & B, having found the former center, you will have drawn the arc, you will have the hourly lines sought; to which you put the numbers of the hours in the order in which you see it done in the figure. You will inscribe the parallels of the fixed stars to their altitudes above the horizon, so that the rising and setting can be traced by this energy. In the semicircles CAD, & CBD, you will connect each quino, & quino degrees, equally removed from the points C, & D in either direction, by straight lines, and you will have all the parallels of the fixed stars. Wherein indeed the planisphere is thus duly delineated; With this technique you will make a magnetic net to be placed over it. In some transparent or translucent material such as the thinnest leaf of starite, which in others is called Mariana ice, the Italian Talcum in this thin leaf may be and you shall describe the circle LMNO equal to the meridian circle ABCD of the plane of the plane a little earlier: which if you divide militarily into 4 quadrants, so nevertheless, viz. in figure v. you see it is done. Inside the semicircle, the vertical lines which we call the Azimuth, and the horizontal ones, which we call Almucantaras, you will inscribe in this way: each of the fives, and each of the degrees from the points LMequally distant in both, & quinos grad. in the semicircles NLO, & NMO, on both sides equally distant from M, connecting the hidden straight lines, see where the line LM will intersect: for the intersections of the pearls, and the pole of both, NO, if you draw an arc from the LM points, you will have the question. And between the other horizontal sine there will be ilsa Crepusculina, with which the 18th degree has joined below the LM, which we express as a capital idea. Having prepared the network in this way, you will adjust the magnetic visor with the length of the diameter of the circle LMNO above the line LMita, i.e. an ice sheet

icily balanced to the movement of the versorij, not unlike the Nautical Rose; When this is done, this verticer refers to the movable horizon, to which the vertical lines drawn from each pole normally insist upon it; with horizontal circles always parallel to the same; You will therefore place this magnetic net with a spike embedded in the center of the sphere in such a way that it can fluctuate freely from here to there; and the magnetic planisphere will be absolute in all numbers, the surface of which remains for several propositions, as we shall declare. His instruments. PROPOSAL I. To find the degree of the Sun in the Zodiac. Two other circles are attached to the limb ABCD, one of which contains the Zodiac, the other the months, in the manner in which it is usually done in Astrolabes, and on the horizon of the armillary sphere; the degree which corresponds to this in the circle of signs will be the desired degree of the Sun, which the apex of the versorij precisely indicates. PROPOSITION II. To find the rising and setting of the sun, and the stars. Yra Planisphere, until the apex of the versorij M corresponds to the degree of elevation of the pole of your region, and then the whole versorium LM refers to this position the horizon of the place of the given latitude. the point of intersection occurs, it shows the hour of sunrise or sunset; that if the hourly line does not precisely touch the point of rising, then see which of the lines of the quarters touches the same point, then on that one the star will rise. PROPOSITION III. To find the number of days and nights. Viescente, viz.

Described by the sun, it touches the horizon or its opposite, and from this point count the hourly spaces towards the meridian, and you will have a semi-diurnal arc in hours, which if you double, you will have the amount of a day; the remainder of the parallel below the vertices, or extending the horizon to the subterranean meridian, will give double the quantity of the night. PROPOSITION IV. To find the declination of the Sun, & the Stars at any time. Having placed the verso LM above the Equinoctial, see what degree in the quadrants CACB, or the parallel DA DB, which the Sun or Star describes at any given time, will intersect, for that will be the required degree of declination. ROPOSITION V. To find the Meridian Altitude of the Sun at any time. Cyra plane sphere, until the magnetic horizon LM rests on the Idatus elevation of the Pole; then observe which degree in the quadrant of the network LN is parallel to the Sun, which at that time the Sun or any other Star describes will intersect, for this will be the height of the Sun or of the Star sought. PROPOSITION VI. To detect the height of the Sun or the Stars at any hour. By moving before the magnetic grid, see where for a given time the parallel of the Sun, or of a star, will intersect the line of a given hour in the plane sphere: for a line parallel to the horizon in a transparent grid, which touches the same point, will give the height of the Sun or Star above the horizon sought for that time. PROPOSITION VII. To find in what vertical circle the Sun, or any Star, dies. Remaining in the same position, see which Azimuthal line is that point on the transparent grid, in which for a given time the parallel of some star and the hour line fall with the horizontal parallel; this or Star quests. PROPOSITION VI. To detect the height of the Sun or the Stars at any hour. By moving before the magnetic grid, see where for a given time the parallel of the Sun, or of a star, will intersect the line of a given hour in the plane sphere: for a line parallel to the horizon in a transparent grid, which touches the same point, will give the height of the Sun or Star above the horizon sought for that time.