Instruments of the Restored Astronomy

EXPLANATION OF THE CONSTRUCTION AND USE.

...toward the [upper] part of the tree, which is the sterile part. By this we imply that nothing can make a person truly blessed or grant eternal immortality except the merit of the Son of God, Christ the Redeemer, and the observance of His doctrine and life. I chose to explain these individual points here—though perhaps they are a bit beside the main point—because of the accompanying illustration. On the other side of the Quadrant, a CanonA mathematical table or set of rules used for calculation. has been engraved with ciphers numbers, which shows with very little effort what the individual points of the Nonnian DivisionA system devised by Pedro Nunes (Petrus Nonnius) using concentric arcs to measure fractions of a degree; it was a precursor to the modern Vernier scale. (which I mentioned earlier) represent in terms of the altitudes being sought.

The use of this Quadrant is for taking the AltitudesThe angular height of a celestial body above the horizon. of the stars and the "Luminaries" the Sun and Moon; this is done when the highest precision is not required, such that knowing the measurement within two or three minutes of a degree is sufficient. One should then direct the plane of the Quadrant toward the star to be observed and properly adjust it by its screws, as was said before, until the plumb lineA weight suspended from a string used to ensure the instrument is perfectly vertical. shows that everything is correctly positioned. Then, the RuleThe alidade or sighting arm, labeled A D in the diagram. A D is raised or lowered until the star is seen through the holes or slits of the dioptraThe sights mounted on the rule., or the light of the Sun is precisely admitted through them. Let the rule then be fixed on the other side near D, where it has a small hidden screw. In this way, the end of the Rule will show the sought Altitude on the outer limb (where the common divisions are) within five minutes; a half or even a third of that roughly 1.5 to 2.5 minutes of arc can be achieved by careful inspection.

But if one wishes to use the Nonnian division at the same time, one must see where the Rule passes some point on those arcs, wherever it may be. One must count which point it is, and how many such points that specific arc contains. With these two numbers, one enters the Table engraved on the other side of the Quadrant laterally; where the two numbers meet in the main area of the table, the Degrees and Minutes revealing the measured Altitude are found. The same thing can be achieved without a Table by using the "Rule of Proportions" the Rule of Three with not much labor: first, take the total number of divisions in the arc where the Rule falls; second, the number 90 for the 90 degrees of a quadrant; and third, the number of the specific point where the Rule rests, counting from the start. Once the usual calculation is performed, the fourth number will show the result sought. In truth, however, this Nonnian method is not sufficient in practice; it does not actually deliver in the result what it promises in theory, as will be clear to anyone who tries it.