Scripta clarissimi mathematici M. Ioannis Regiomontani, de torqueto, astrolabio armillari, regula magna ptolemaica, baculo[que] astronomico, & observationibus cometarum, aucta necessariis, Ioannis Schoneri ... additionibus. Item observationes motuum solis, ac stellarum tam fixarum [qua ...] erraticarum. Item libellus M. Georgii Purbachii de quadrato geometrico ...

It was not my intention to omit this brief problem, even though it does not require a fixed position of the stationary instrument, lest the annual circle seem to have been inserted in vain.

THIRD PROBLEM.

To investigate the true place of the Sun without knowledge of the present day, and simultaneously to express the configuration of the heavens.

In the resolution of this problem, and of all that follow, this one thing, even if it is not openly commanded, must nevertheless be observed first: that the instrument be set up appropriately, as we advised a little earlier. Therefore, with it established, turn the region of the signs here and there; likewise, rotate the crest separately until the ray of the Sun falls upon each hole of the larger ears as correctly as possible, for the head of the ruler of longitude will show the sought-after place of the Sun in the ecliptic sign-bearer. I call the head of the ruler that extremity which is extended toward the celestial ecliptic. Although the resolution of this problem may seem no less brief than easy, it nevertheless has a certain appearance of fluctuating uncertainty because of two different motions of the parts of the instrument adhering to each other, namely the crest and the region of the signs. You will be able to provide against this thing by this conjecture, which is by no means useless. Rotate the region of the signs together with the whole crest until the shadow of the circle of latitude becomes like a straight line, which indeed is accustomed to happen while the plane of the circle of latitude, if it were extended into the immense, would pass through the center of the solar globe. Then, therefore, the solar ray flowing through the anterior ear must be observed next to the posterior ear. For if it has correctly filled the hole of the second ear, the head of the ruler will manifest the place of the Sun in the ecliptic sign-bearer. But if that ray has fallen above the hole of the second ear, the head of the ruler must be transferred to the lower part of the sign-bearer; and likewise, with the region of the signs moved as before, it must be considered if the ray admitted through the anterior ear