In 1510, Copernicus settled in Frombork on Zalew Wiślany, the Vistula sound, the residence of the chapter of Warmia. At once the authorities assigned him different official duties the canons performed in one year term. In the autumn of 1510 he became, both, general vicar and inspector of the chapter. In 1511 he was generał vicar and in charge of the provision fund and finally, during the last office term, from November 8th of 1512, to November 8th of November, 1513, he was only general vicar. Very detailed investigations on the progresses of his studies show that in those days, he did not have yet collected all the empirical materials to write down his work, hut was still organizing his workshop and building the instruments.
All the three instruments were copies on the ptolemaic ones and he probably constructed them in 1512. That is suggested by his notes about the opposition of Mars in June 5th of that year. That observation must have been made with a spherical astrolabe, (so called armillary sphere), the instrument used for the calculation of ecliptical coordinates of stars and planets and for the determination of local time. The construction of the astrolabe is described in the chapter 14th of his 2nd book De Revolutionibus. The observations made in 1515 prove the existence of another two instruments: the "Quadran", and the "Triquetrum", also described in the same work. They could have been contructed at the same time as the astrolabe, because the note about the observations made by their means, does not exclude an earlier use.
A quadrant was a vertical square board, on which the quarter of a circle divided in 90 degrees was drawn, fixed on a perpendicular the center. Copernicus describes it in the 2nd chapter of the 2nd book of De revolutionibus. He describes also the way how to fix it to a special observation plate called "Pavimentum", very carefully levelled horizontally. This plate is marked with a meridian line on which," The piane of the instrument should be put vertically, with the center oriented to the South, in such a way that the plumb line hanging down would osculate along the meridian line under the right angle. During the days of spring and autumn equinoxes, Copernicus observed the shadow of the midday Sun, "cast from the centre by that indicator or the roli, setting something to the ąuarter of the arc just in order to read with major reliability the place of the shadow, in grades and minutes. Once it was done, the arc of the circle between two shadows, casted by the Sun during the summer and winter solstices, would indicate the distance of the tropics and the total angle of inclination of the ecliptic. A half of this angle gives the distance between each of the tropics and the equator, and the angle of inclination of the eąuator to the circle passing through the centrę of the signs of Zodiac". Finally, the last instrument, made of wood as the other ones, called Triquetum" or "parallactic instrument", is describedby Copernicus in the chapter 15, book 4. It was composed of three stips that made an isoceles triangle with a variable base. One vertical arm was fastened with hinges to the stand, while the other one, with two sighting vanes, was an axis of sighting and could take any position in the vertical plane. The third strip was scaled with units one thousandth of the length of tho other two arms. To determine the distance of a star from the vertex point, at the moment when itis seen dirctly in the sighting vanes, one lays the bottom strip with the scale and checks how many units whose number in the diametre of the circle is, are cotained in the angle between the eye radius and the level axis; the circle is 2 000, now, with the table of chords one can find the needed arc of the great circle between the star and the vertex point. (Woszczyk
The last of the basic elements of his scientific workshop in Frombork was a house called canonical curia ( curia canonicalis), which was situated outside the walls enclosing the cathedral, outside the moat, among other curias and, like all of them, surrounded with a garden. In that garden, Copernicus built the above mentioned observation plate (pavimentum) that overlasted many years after his death. In 1584 a Danish Astronomer, Tycho de Brahe, sent to Frombork his assistant Elias Cimber to check the rigour of some of Copernicus' observations. Cimber found the pavimentum without problems and had only to ascertain the position of the meridian line to be able to start making the needed measurements. So the place of work of Copernicus was strongly connected with his place of work, with his observatory (Pagaczewski 1964:1967; Sikorski 1969).
In the midyear of 1513, when Copernicus was still a vicar general of the chapter, he received an unexpected honor: Paul of Middleburg, bishop of Fossombrone sent him a letter with a request to take part in the refarming of the calendar. The explanation was clear: The contact was arranged through the mediation of Bernard Scultetus, dean of the chapter in the years 1499-1518, and in those days a scribe of the 2nd Council of Latran.
Copernicus treated the appeal very seriously. We know it not only from the character of the investigations he started those days, but also from his own words in the preface of De revolutionibus: not very long time ago, during the papacy of Leon X, the council of Latran was discussing the problem of the reformation of the calendar; it was left without solution because there were not any exact measurements of years, months and motion of the Sun and the Moon. Since then, encouraged by the eminent personage, Mister Paul, bishop of Fossombrone, who controlled then the problem in question, I started to strain my brain just to examine those things better. Needless to say he wanted to examine those things on the base of his own theory as soon as possible.
The year of 1513, in which he received the unexpected encouragement from the council, also had an happy and unusual conclusion: on the 8th of November, the third term of his vicar's office came to an end and there is no information that he was assigned any other function. This seemed so incredible that is appeared necessary to search thoroughly everything that remained in the archives to make it sure. In such a situation, a question emerges: what could have been behind this? Probably he got a vacation" of some kind in order to come up to the expectations of the reverent bishop Paul of Middleburg, in other words, to start working!
The first year free of duties he settled down in a canonical curia chosen by himself, which means that he obtained the best possible conditions for his work. In February he determined the position of Saturn in order to find its distance from the Sun, and in May he observed also the opposition of that planet, by the help of the observation plate, on which he set the astrolabe. By means of the quadrant he determined the latitude of Frombork (Birkenmajer 1900:317, 294-295). The results of those observations will be written later in his work.
The next year he started, with the help of the quadrant, a year long series of observations of the solar motion (11th March 1515- 11th March 1516), in order to establish yhe magnitude of the precession and the longitude of the sidereal year. For that purpose he chose not only the moment of the spring equinox, but also some other positions of the Sun, suitable and easy for observation: the middle of Taurus (26th of April), the middle of Leo (29th of July) and the middle of Scorpio (29th of October). He determined the autumn equinox on the 14th of September. At the same time, the chapter decided to take care of the state of the mechanical clock on the cathedral roof. As some investigators say, it could mean that Copernicus works, connected with the reformation of the calendar, met with the official approval (Birkenmajer 1924:276; Brachvogel 1925:37).            
On the third year free of duties he observed the Sun in the middle of Aquarius (26th January 1516) and the moment of the spring equinox (11th March). After two years of observations, the results of which were published in De revolutionibus, he discovered the motion of the solar apogee in relation to the fixed stars, and some changes of the eccentric of the Earth. He also discovered that the vernal point of the Sun had shifted, since Ptolemy's epoch, more than 30 degrees. Those findings gave him the possibility to formulatethe theory of the apparent motion of the Sun (Birkenmajer 1900: 163,165,302,317,318; M. Kamienski 1963:96-97).
In that situation he was ready to write down his work. First he wanted to publish only the tables, without any description, but he did not manage to realize that plan. On the 8th of November, 1516, during the extraordinary session of the chapter, in which Copernicus took part, the administrator of the common property renounced his post. The exeptionality of the situation consisted in the fact that the term for holding such an important office usually lasted no less than three years, so nobody expected this sudden necessity to designate a new administrator. Christopher Suchten, who had quit the post, was excused for desease, and obtained free time for his treatment. In 1519 he would not any more among the living ones (Oracki 1988:169-170), and Copernicus was chosen as the new administrator.
The seat of the administrator of the common property (bonorum communicum), i.e. the land property of the Chapter, was Olsztyn castle, 80 km. distant of Frombork. The removal to Olsztyn was unexpected for Copernicus. The 8th of November 1516 he stood face to face with the necessity to leave his home for three years immediatly, practically from one day to the next (for instance M. Launau in the years 1483-1490, Baltazar Stockfisch in 1494-1502, Jerzy Delau in 1503-1508, Tiedeman Giese in 1510-1516). The archives of Warmia Diocese in Olsztyn, ADWO, the files of the Chapter L92 (cards 28-40' II 55, cards 43-74,74-77,78-81,99-100.). The whole period of his administration is dated by the settler's work he did there. For a great part, they consist of notes, made by himself, that remain till now in fascicules. In fact, they are, after De revolutionibus his second most important manuscript, only recently published tenement villages of the Chapter, the description of the amount and the way of paying the rents together with the determination of the extant of apportionment of Land and the specfication of the appropriated agricultural tools, livestock and dead stock, and the indication of witnesses and guarantors.
Copernicus, at all rates wanted to proceed with the investigations he had started in Frombork and used all of his ingeniousity to realize it. As a proof of it we can still see in the cloister of the castle the authentic proof of his work - an astronomicall board of dimensions 140 x 705 cm., an immovable astronomical instrument, the fourth Copernicus possessed (Pagaczewski 1966:146; Woszczyk 1973:31). The direct visual contact with an artefact that undoubtedly was made by the great astronomer provokes comprehensible emotions. Such emotions grow even more if we consider that the monument overlasted many destructive wars as if by miracle. It did not share either the lot of so many other monuments that were treated by their users, especially in the nineteenth century, with an exeptional carelessness and lack of understanding of the values left by anterior generations. Unfortunately, however, that attitude decided also partly on the actual state of the maintenance of the board: at some time it was painted with lime and divided by transversal partition walls. The exposure and the preservation of what is the real product of Copernicus' hands was made possible due to the competence of contemporary conservators of monuments, the team of Professor Bohdan Marconi from Warsaw, who worked here in the years 1956-1957.
Copernicus did not need to choose or look for the place of this board, it just presented itself. Now we can understand it better thanks to the mentionned investigations of preservation and the scientific investigations led in the year 1955 by the well known (in Poland) horographer, assistant professor Tadeusz Przypkowski the astronomer, prof. Fryderyk Koebeke, and also to the complex of architectonic and preservation investigations led in the castle during the tears 1984-1986 that allowed the reconstruction of its original shape (Przypkowski 1960:138-160; Madeja-Kulecka 1984-86). Some details connected with the environement in which the board was situated, were compleyted at my request by Mrs. Małgorzata Okulicz, an art historian at the Museum f Olsztyn castle.
The astronomical instrument from Olsztyn is a kind of an empirical table. It possesses all the qualities that allowed to lead- or maybe to continue- the investigations of the inequality of the motion of the earth. Copernicus was not entirely conscious of the reasons of those inequalities, although he distinguished phenomena that resulted from them. As we know, he could exactly calculate the equation of time which was for him just a reflection of the inequality in the annual circulation of the Earth around the Sun. And similarly trying to explain the phenomenon of the constant shift of the points of equinoxes (so called precession) on the ecliptic, he based it nghtly on his heory (Copernicus 1953:ch.11, lib.l). The observation of precession was connected necessity of the investigation of the moments of equinoxes coperniclogists, L.A. Birkenmajer says, it was one of the most important investigation
works of Copernicus (Birkenmajer 1900.302). This conclusion corresponds of the chronology of the origin of the manuscript De revolutionibus Copernicus started to write his work with the above mentionned question (The book Nr.l of the De revolutionibus was written exactly on the schema of the first book of the Almagest of Ptolemy., Copernicus possessed the 1515 Venice edition (Birkenmaier 1900:95; Jarzebowski 1971:37).
The observation of the Sun and the works on the inequalities of the circulation of the Earth were the main object of the research works of Copernicus in Olsztyn; at the same time it was the continuation of the works started in Frombork (Dobrzycki 1968:8). In Olsztyn, however, Copernicus probably did not need the observations of the moments of equinoxes to follow the phenomenon of the precession, but to find the divergences of these moments with the julian calendar. He was interested simply in the problem of telling the time lenght of the year. The question was to find the real moment of the spring equinoxe, the date of which was changing in the calendar over the centuries because of the differences between the calendar year that had 365,25 days and the real period of the Earth circulation around the Sun, so called astronomical (tropical)year, lasting 365 days, 5 hours, 48 minutes and 46 seconds, and being thus 11 minutes shorter than the calendar year. Since the Council of Nicea in the year of AD 325, when the moment of the spring equinox had been established on the 21st of March, it had regressed so much, that in the days of Copernicus it fell on the 11th of March. Therefore, Copernicus tended to find the lenght of the astronomical year, measured by two consecutive moments of the equinoxes.
To measure the height of the Sun in Frombork, he used the quadrant, set up on the observational plate in the garden of his house. In Olsztyn, however, he could find no quiet place in the open air within the limited space of the castle court. The castle combined defensory service and judicatory functions as it was the residence not only of the administrator of the chapter property, but also of the burgrave, who had under command a military crew of guards. The castle lived certainly an own intense inner life. The idea of setting the quadrant up dirctly at the court, on the special observatory plate, was out of thequestion. Resigning of the quadrant, Copernicus had to find another solution that could be adapted to the conditions at disposal. That is why he came in the end to the construction of his own, original instrument which could be placed quite out of the way, immovable, and moreover, very close to his dwelling place (Sikorski 1973:112). The main requirement of the investigations made with the help of that instrument was the acess of the sun light to it. How could that requirement be made? - The Olsztyn castle was composed as we can see up to day, of two parallel, many storeyed wings, covered with a high roof. Those wings are situated more or less on the axis South-East, North-West, what means that the left one, seen from the entrance, from South-East, was lighted by the Sun in the major part of the day on its outside wall, while the right one was receiving the solar rays mostly onto its inside wall, seen from the court. The court was a little irregularly shaped as a square with sides of 33 meters, limited by the two castle wings and the curtain walls, 12 meters high, between the ends of the wings. The square was not so deep as not to allow the sunlight come in. On the contrary, even at the lowest yearly position of the Sun, it fell obliquely on the inside wall of the right wing, getting there over the curtain wall already in the morning. But in the afternoon the light could hardly pass over the roof of the left wing, and in the North-West corner of the square it met on its way an insuperable obstacle: a cylindrical tower, 30 mts high, 9,2 mts. in diameter. Fortunately the administrator's flat was on the first floor of the right repredentative wing. All the windows of that wing were opened on the other side, over the moat, to the North-East. Only two windows in this gable walls looked on North-East, One from Copernicus'flat and one from the chapel. From the point of view of the astronomer, those windows were useless, he would care only about the part of wall illuminated by the Sun.
Copernicus settled down there and at once started to work, most probably already in November 1516, it means immediately after his arrival to Olsztyn. We may suppose it because, as we will state in a while, just on the 25th of January 1517 he started to observe the orbit of the Sun on his table. But it had been necessary to prepare the wall before. As the plasterer's work was impossible during winter time,the plaster must have been laid before the first frosts, around the end of November.
The conservators' investigations showed that the table consists of two layers (Mrs. Maria Orthwein, Archives of the Section of the National Service of Protection of Monuments in Olsztyn.). It means, the second was a leveling of the first, probably at copernicus; request. Perhaps at the time of preparative plastering, the astronomer was not able to determinate exactly what surface of the wall the graph would occupy, that is why the leveling coat was laid in excess, beyond the extent of the later graph, but to which extent, it is difficult to state surely now as the plasters were removed in 1911.
The investigations of T. Przypkowski have shown beyond any doubt that the graph was made by the projection of the solar light reflected by a mirror. The mirror must have been installed on the lower wall of the gallery, on the window-sill of one of the arcades; approximately, because it was not founded empirically, on the second or third arcade counting from the left. The table occupies nearly exactly the space opposite to the second and third arcade. To define it more precisely we must find the lever of the window-sill in those days. The most certain calculations place this level 140 cm from the top of the arcade (it is now 170 cm).
Watching the table, we see many lines drunning diagonally from the upper left to the lower right. All of them, but one, are red. they were drown every five days, following the movement of the solar rays reflected by the minor. Each of them starts at the moment of the Sun's culmination and runs down as the Sun's altitude decreases. Those lines, marking segments of the Sun;s path are hyperbolical, but so obtuse that they approach straightness. But only one of them was really straight, Copernicus marked it with blue color and inscripted there carefully: AEQUINOCTIUM, with renaissance capital letters with serives. Only three of the letters are left, the first one ressembles a T, but is in fact a part of the latin diphtong AE, according to T. Przypkowski who deciphered the inscription more easily once he had understood the function of the table. This line marking the passage of the Sun on the Equator was precisely what Copernicus was searching. Accompanying the hyperbolical red lines/ he inscribed arabic numbers in groups of five units from 0 to 30, starting both ways from the equinoxial line, that division reflects the zodiacal division of the Ecliptic.
As we have stated, the graph was undoubtedly drown at the very beginning of the astronomer stay at Olsztyn castle in 1517, in the period bracketing the vernal equinox, and as we know the sun passed the vernal point that year on 11th of arch, it is easy to find on which days the different lines were traced, every five days from January 25th to April 20th. If we compare those dates with those of his administrative travels to place the settlers, we see that only two of them interfere with the days planned for observations of the light spot on the table, while all the rest alternate.
It seems obvious that not all of the lines resulted from direct obsevations, but if one day or the other the sky was covered, the missing hyperbola could be reconstructed on the ground of calculation and extrapolation from the other ones. But most of the table must have been constructed empirically. S. Pagaczewski describes the method in this way: When on any place of the table, some time before or after the vernal or autumnal equinox, at a given moment, the reflection of a sunbeam in the mercury mirror appeared, Copernicus could mark the place with a lead pencil and by the help of graphical interpolation, find how long time before or after the equinox the observation was made. The aritmetical mean of a few or a dozen or so observations of that kind permuted to establish the ever age moment of the equinox and the lenght of the tropical year, in comparison to the earlier observation. The same results, He had obtained in Frombork by the help of the quadrant (Pagaczewski 1967:56).
The slope of the equinoxial line of the Olsztyn table was studied by Tadeusz Przypkowski and Fryderyk Koebke, on the ground of their own countings. They took the azimuth of the wall, 33° and 3' West of South, and the latitude of Olsztyn equal to 53° 46' 36" but estimated by Copernicus 53° 45' and they found with astonishment that the equinoxial line was corresponding exactly to the one of the graph. T. Przypkowski, surprised with that result suggested that Copernicus did not use a real mirror, too small to be levelled with exactitude, but rather a vase filled with mercury or even some dark red wine, fixed in a hole (Przypkowski 1960:56). In his opinion, Copernicus table is the oldest known example of use of gnomonic reflection: the special conditions of the gallery and the opportunity of using the space of the wall over the door, close to his appartment, fertilized the ingenious and creative mind of Copernicus and resulted in the first use of gnomonic reflection. (Przypkowski 1960:152)
The conservation work has shown that already in the sixteenth century, someone tried with persistence to find in the table a sort of sundial, an amateur unsuccesfuH trial. In this attempt, that person erased and scratched out the numerals inscribed by Copernicus at the bottom of the table and reproduced higher, directly on the graph, and under, he put the Roman numerals for hours. Those numerals correspond to the black lines that were added. Nevertheless, those additions were not corrected because of the eventuality that they could have been made during Copernicus lifetime, although without his contribution (Przypkowski 1960:159-160).
Leaving Olsztyn, Copernicus left the carefully drawn table, a result of his investigations, but at that time already useless. Was it left as a decoration? did anybody ask him not to destroy it? Maybe someone wanted to keep it as a testimony of the long astronomer's stay in the castle? and maybe just for that memory or to keep it alive ,the person took the effort of making use of the table, though unsuccessfully, and by the use of the mirror tried to adapt it as a Sundial. That person must have worked hard but could not master the insubordinate motion of the Sun, he came to the point of installing two mirrors to reckon the time, says Przypkowski. Copernicus never knew about it (Przypkowski 1960:159). The sundials were of no interest to him as we have not trace of any ihe would have built in the cities he visited, although here and there folk traditions repeat such stories up to day.
Jerzy Sikorski