Instruments of the Restored Astronomy

EXPLANATION OF THE CONSTRUCTION AND USE.

This Quadrant, marked A B C, is also made of solid brass original: Orichalco; it is arranged as shown in the figure, having beneath it a Horizon G H I K containing the AzimuthsThe horizontal angle or direction of a celestial body, measured around the horizon from the north or south., which is also cast from solid brass. The individual parts of the entire instrument are explained as follows: from the Center A to B or C is a length of one cubit and a half Roughly 2.2 to 2.7 feet (68-83 cm), depending on the specific cubit used.. From this, the circumference B C is visible, which is subdivided into individual minutes of the degrees by transversal points in our usual manner. It employs no other method of distinction, unlike the previous instrument, because the limb is not wide enough to comfortably accommodate more. It nevertheless has a width of about two fingers and is capable of expressing individual minutes transversally, as I have said.

The square that is seen in the area of the Quadrant A D E F, together with the cross-bracing supports meeting it, are fitted there primarily for the sake of support and greater firmness. However, that Square can also be used for geometric dimensionsTerrestrial surveying, such as measuring the height of a tower or the width of a valley. regarding the height and width of things seen on the earth that have been built by human labor. This is the same way that the instrument which PeurbachiusGeorg von Peurbach (1423–1461), a hugely influential Austrian astronomer and instrument maker. called the Geometric Square provides these and similar measurements, as explained and demonstrated by that eminent man in a specific book. Elsewhere, this is indicated with less effort (though not as exactly) by those who explain the AstrolabeA portable medieval instrument used for timekeeping and surveying., particularly regarding what they call its "back."

Another fitting seen around these parts, which is understood to be on the back of the Quadrant, represents the shape of the letter Y and is marked with these three letters V V X Y. It is present so that the plane of the Quadrant itself may stand at a right angle to the Horizon in which it is encased, no matter how it is rotated. At the part where it joins the Horizon near Y, it is fixed by a small screw when necessary, so that by remaining unmoved in its place, it may conveniently show the Azimuthal degrees. There is also a certain Rule A support bar. drawn from the Center L toward the screw Y that joins the end of the support with the lower and middle part of the Quadrant, so that everything may hold together more firmly and be rotated as one. A small lead weight original: plumeolâ is also added below at the screw so that the Quadrant may stand still in any place without any wobbling.

The fact that this Quadrant is not solid across its entire surface, but has those openings (mostly four-sided) seen within it, offers the advantage of being lighter in weight. Because of this, it is not only easier to handle but can also be moved from one place to another (for which reason it is built from several parts), as we will indicate more fully later.

Regarding its rule carrying the dioptraThe sighting bar or alidade used to align with stars., we will speak of it shortly, after we have explained a few things about the Azimuthal Horizon. Indeed, those sights serve equally for the observation of both Altitudes and Azimuths. Therefore, the Rule itself, with its longer and wider plane, lies flat against the plane of the Quadrant everywhere; so much so that even at its lower part where it projects at A S, it precisely faces the same flat surface, and the sights with their pinnacidiaThe vane-sights or small plates with slits used for precise aiming. are equidistant from this and stand at right angles to it. Otherwise, an accurate investigation of the Azimuths (to say nothing of the Altitudes) could not be made.

The Azimuthal Horizon (which I mentioned) located below the Quadrant and supporting it is expressed by G H I K. It has cross-supports at right angles so that it remains firmer, and the Quadrant rotates entirely within a channel fitted there around the common angles of these supports, namely in the center of that same Horizontal circle. Furthermore, it has four screws M N O P near the ends of these supports, by which the entire horizon (and thus the Quadrant standing upon it) may be directed so that the plane of any vertical circle is perfectly imitated. This ensures the equilibrium of the Horizon, so that the use of both regarding Altitudes and Azimuths is correctly established.

The Rule S V T applied to the Quadrant (which I mentioned slightly before) functions in the same way with its sights and vane-sights as indicated in the previous description, except that below, near the sight S, it has two handles original: ansas by which it can be conveniently raised and lowered by hand as the altitude to be observed requires. This also allows its own weight to hold the other part of the Rule T as if in balance.

Moreover, the whole instrument stands upon a square stone, hollowed out somewhat on the sides for more convenient use, which is expressed by the letter Q. This stone rests firmly upon a stone column R, as this figure sufficiently shows. In its construction, this Quadrant has an advantage over the previous one: both it and the Horizon on which it stands, and all other things belonging to it, can easily be taken apart and put back together again. It is suitable for being carried from one place to another in a convenient case, as it does not consist of as many parts as the previous one. These parts, through screws arranged here and there, allow not only for disassembly but also for easy reassembly into the exact same plane as before. Therefore, I am accustomed to calling this the Portable Azimuthal Quadrant.