Giuseppe Campani telescope and lens maker

The respected permanent place in the history of astronomy achieved by Giuseppe Campani unquestionably owed much to the numerous celestial discoveries made by others with his lenses and telescopes, especially by Jean Domenico Cassini, and due to a degree to the astronomer’s confirmation of the instrument maker’s observations and his repeated acknowledgment of the superior quality of Campani’s instruments. It was a situation of mutual gain, for it was largely the superior excellence of Campani’s lenses that contributed to Cassini successful astronomical discoveries, and it was because Cassini was able to do so that Campani’s career became firmly established.

Having heard mention in 1661 or 1662 of a new telescope said to have excelled all others, Cassini undoubtedly was among those who sought to meet the newcomer so he could test one of his instruments. At the same time that Cassini was impatient to identify and meet the telescope maker, Giuseppe was just as eager to meet the popular astronomer. Cassini became aware of the developing conflict and contest between Divini and Campani, and he happened to be on the scene when the first inconclusive trial of the telescopes was held, during which Campani allowed him use of his telescopes. It was with a Campani telescope that Cassini eventually made some of his important astronomical observations of Saturn and Jupiter. And it was with a Campani telescope that he was to detect the rotations of Mars and Venus.

The year 1664, in addition to having become known as the year of the comet, also was a period during which studies were being made of the planet Jupiter and its satellites. It was in the summer of 1664, according to Cassini’s account, that he received the abovementioned invitation from Giuseppe Campani “to Monte Citorio to observe Jupiter together with a number of personages of distinction who are gathered there to test out his telescopes, and forthwith that I saw this star I observed two spots on its disk comparable to the configuration of the satellites resulting of those I had seen the previous day and I realized that they were the shadows of two satellites that traversed the disk of Jupiter that was exposed to our view. Cassini had combined the excellent object lens of focal length 17 feet that Campani had given him with a suitable ocular lens into a telescope that he used during his travels to Tuscany. With it, in July 1665, he discovered the permanent spots upon Jupiter. As previously noted, a study of these spots is what enabled him to determine the duration of the rotation of Jupiter upon its axis, which proved to have been excellent.

After having become well known within a very brief period for the high quality of his lenses and telescopes, Giuseppe Campani gradually also began to achieve recognition as an astronomer. This was as a consequence of a series of observations he made by using his own instruments. Although these astronomical observations personally made by Campani were less prominently acknowledged than were the widely heralded achievements of Cassini, they nonetheless constituted an important if indirect contribution to contemporary astronomical knowledge.

The discovery of the Jovian satellites was widely acclaimed, and it was described by a writer in the Journal des Sçavans in 1666 as being “one of the most wonderful that had as yet been made in the sky”, and “one that required research to determine whether the phenomenon observed for the major planets was common as well in other components of the solar system. Giuseppe Campani had the opportunity to cooperate closely with Cassini in this endeavor, with one of his own telescopes of 50 palms. It had a focal distance of more than 10 meters, which was exceptional for an instrument of that period. Cassini’s observations were confirmed in Rome by Campani.

News of Campani’s achievements in astronomy became more and more widely known, and their importance was increasingly recognized during the later decades of the seventeenth century. As noted, his growing fame was partially due to the success of his own astronomical observations as well as to his collaboration with Cassini but chiefly as a consequence of the outstanding superiority of his lenses. Astronomical observations made by Campani himself did in fact help to promote and publicize the excellence of his instruments. In order to evaluate Campani’s contributions in astronomy, it is necessary to study his observations as a separate aspect of his activities. According to Nicodemo Jadanza, a nineteenth century historian, a contemporary analysis of Campani’s observations was voiced by Huygens who spoke of Campani as a “marvelous observer” and stated furthermore that to Campani must be attributed some important discoveries of his own in this field that previously had not been recognized.

The late Professor Guido Horn d’Arturo, then director of the observatory at the University of Bologna, also rated Campani as a capable observer, in addition to considering him to be the maker of the finest astronomical instruments of his time. He maintained that Campani had determined the rotation of Jupiter and the division of the ring of Saturn at the same time as Cassini had done and possibly even prior to Cassini. It is difficult to determine whether Cassini or Campani actually was the first to identify “the other little planets,” that is, the much smaller satellites of Jupiter that Galileo had not succeeded in observing.

Auzout, who himself was a maker of astronomical lenses, could do no less than admit that

never before had he ever seen lenses as clear and polished as those made by Campani. The matter so aroused the curiosity of Huygens, it is said, that, in 1666, he had traveled to Paris to examine personally the Campani telescope. His judgment, expressed in a letter to his brother Constantijn, is sufficiently important to quote: “The beauty of the Campani telescope at the home of the Abbé Charles”, he wrote, “consists in that it is without colors of iris [chromatic astigmatism], that one perceives point of points in ocular glass; that the opening is sufficiently large without, however, that the objects appear at all bent or warped, and that it represents ] very distinctly because of the good quality of his glasses.

Huygens had examined the instrument with considerable attention and reported all technical details. He had taken note of every one of its measurements and set to work to produce an instrument having similar specifications. It appears that he had experienced some difficulty in marking the fine glass and in obtaining a good form or mold for constructing the object lenses, as Huygens himself later recounted. It was formed in a fashion illustrated in a sketch by Marco Tappi, the first lens having a distance from the second that was double their communal focal distance.

The eyepiece was composed of three perfectly equal lenses of one inch [pouce] and 10 lines of focus (4.79 cm). The objective had a focus of 2 feet and 4 inches (75 cm), and the total length of the instrument was 3 feet and 3 inches (102 cm). The aperture, however, was 19 cm, the diameter was 17 mm, the distance from the eye to the first ocular lens was 39 mm, from the first to the second, 93 mm, and from the second to the third, 100 mm. The measurement was expressed in feet used in the land of the river Rhine.

The optical system of the first two lenses of Campani’s telescope was telescopic, and had reerected the image formed in the objective without altering its dimensions. The finer quality of the telescope was therefore due to the telescopic system contained in the eyepiece, to the absence of chromatic aberrations,astigmatism and the absence of spherical aberration. These qualities, now noted by Huygens, had already been reported by Campani in his Ragguaglio in 1664.

Giuseppe Campani Objective lens 107.5 mm diam, 3.2 mm gr, 9.4m FL.

Giuseppe Campani drawings of Jupiter moons shadows and Saturn rings.

Giuseppe Campani terrestrial telescope deisgn

PARIS OBSERVATORY Objective lenses History

Immediately upon his arrival, Cassini set out in search of lodgings and had been directed to the King’s Library, where he expected he would be able to remain. He was warmly greeted by Pierre De Carcavi, the King’s librarian, a mathematician and an Academician. He was informed, however, that no room presently was available on the library premises. All of its space was already occupied by Carcavi and his family and by the celebrated Christiaan Huygens, who had been invited to Paris by Colbert 3 years earlier and had been immediately lodged in the King’s Library.

It became apparent at once to Cassini and to others that in the original planning of the observatory, which was currently under construction, no provision had been included for lodgings for the astronomers, neither in the completed observatory nor elsewhere during the interim while they were awaiting the structure’s completion. When Colbert was informed of the lack of accommodations for Cassini, however, he promptly ordered that a habitation was to be prepared for him in the Louvre gallery, the development of which was under the supervision of the architect Claude Perrault (1613–1688).

Cassini had expected to begin work as soon as the observatory could be made habitable, but the extended delay that lay before him made him increasingly impatient. Furthermore, the lodgings he had been assigned at the Louvre proved to be most uncomfortable. He thereupon proceeded to make his own arrangements and rented a house at Ville-l’Évéque, a short distance from the western gate of Paris. There he was pleased to find that the rental included a garden in which he could install his instruments and from which he would be able to make his observations. At the time that he had departed from Bologna to Paris, he had expected his absence to be for a limited period, and consequently he had brought with him only his favorite telescope, the one having a focal length of 17 feet that Campani had given him; it is to be noted that, although several references made by contemporaries to this same telescope stated varying lengths, it had a focal length of 17 Roman palms (379 cm).

Immediately upon moving into the new quarters that he had found, Cassini lost no time before turning his eyes to the skies and beginning to search them with his prized Campani telescope. With it, while he was still in Italy, he had discovered the rotation of Jupiter and of Mars around their own axes, in addition to the eclipses of the sun by Jupiter’s satellites. The same instrument in France provided him with his first glimpse of Iapetus, Saturn’s second satellite. And again several years later, in 1672, it was with a 50 palms Campani lens that he had located the third satellite, Rhea. This first grand result, the discovery of Iapetus, a new satellite of Saturn, proved to be of considerable interest, and the French Académie, and particularly Colbert, remained greatly impressed by the excellence of this Campani instrument with which it had been achieved. At that time, there was the general belief in France that all that still remained unknown about the heavens could be discovered with telescopes of the greatest length. A we shall see, Colbert then proposed henceforth to equip the recently founded observatory entirely with these instruments and ordered Campani to send to France the largest and most excellent telescope that he was able to make and to continue to perfect his art in order to make them longer.

Paris Observatory 17th century 20 foot and 5 foot telescopes 1679

Paris Observatory 34 feet telescope

In Rome, meanwhile, Giuseppe Campani soon found himself occupied almost entirely with commissions from the Sun King to provide lenses and telescopes for the Paris Observatory.

These were assignments to which he had to give priority, a situation that would continue during the major part of the next decade. It was through César d’Estrées, bishop of Laon, that Colbert conveyed his orders for lenses to both Divini and Campani, the artisans in Rome. The bishop was entrusted with various missions of particular sensitivity at the papal court in Rome. In fact, in an earlier period, César d’Estrées had operated in secret in fear of the Pontiff’s displeasure.

Colbert’s instructions to d’Estrées made eminently clear that he was to commission as much work for lenses and telescopes from Campani as he was capable, and that he could offer as enticement the fact that “besides the advantage he will have in selling them, the King will make him a substantial present”. In the course of the next few years, Colbert was to be responsible for having materially assisted the development of the Paris observatory and its shift from the use of traditional instruments to the newly conceived tubeless telescopes by providing more money for lenses and less for mounts. Campani complied with Colbert’s urgings by producing an object lens having a focal length of 34 feet for which he received payment of 1000 eçus. It was with these Campani lenses that Cassini discovered two new satellites of Saturn: as we shall see, he had found the first of them in October 1671 with the lens of 17 palms and the second in December 1672 with the lens of 34 feet. Three years later, in 1675, he was to discover the division of Saturn’s ring, which now bears his name. Throughout this period, Cassini managed to make observations also from the gardens of the Abbaye de Saint-Martin-des-Champs, which subsequently housed the Conservatoire des Arts et Metiers.

The outstanding quality of Campani’s lenses, despite the fact that Cassini’s discoveries attested to it, had not been acknowledged at first in the Academie without discussion. The Academicians involved with astronomy—Cassini, the Abbé Jean Picard, Olé Roemer, Carcavi, Huygens, and Claude Perrault—often gathered together at the observatory to make comparative tests of object lenses produced by French and Dutch makers with those made by Divini and Campani. Many of these tests that were being made for the purpose of comparing telescopes were held in the presence of the foremost French optical instrument makers, and each time the Italian lenses proved to be superior to all others.

Colbert did not dared to take part in these discussions, although he expressed considerable interest in the conclusions reached by others. The Italian telescopes were invariably of better quality than those constructed by the French and the Dutch makers, yet the latter instrument makers insisted on constructing ever-larger telescopes. In his history of the telescope, Henry King noted that Nicolas Hartsoeker constructed lenses having focal lengths of 155 and 220 feet, while lenses made by Auzout actually arrived at focal lengths of 300 and 600 feet (approximately 200 meters). It finally became apparent to the observers using the instruments that it was not only the focal length of the lenses that made the Italian ones superior. Eventually, even Colbert himself prized the Italian telescopes much more highly than did the others at the Académie, despite the claims of the French optical instrument makers, and in particular of Pierre Borel, who poorly supported the superiority of the Italian object lenses over those that he made.

At the end of October 1671, again using his Campani telescope, as previously noted, Cassini also discovered a satellite of Saturn, the first since Titan. It had occurred in December 1672, only a few days after his installation at the Paris Observatoire, that he discovered another of Saturn’s satellites with his telescope of 34 feet. In his report of these observations, which he did not present until January 14, 1705, Cassini noted:

That [telescope] which served us for the discovery of the new Phase of Saturn, which of this Satellite was of 17 feet, and which had been given to us as very excellent by M. Campani. This was the same telescope that we used to discover the revolutions of Jupiter and of Mars on their axes, and the Eclipses of the Sun in Jupiter made by the interposition of the Satellites.

It was judged that by the lunettes of one that was larger we would be able to see that Planet, when one ceased to see it by means of the one we have been using. It was for this reason that M. Colbert gave the order to M. Campani to send as soon as possible the largest and the finest that he had, and to endeavor at the same time to perfect his art, in order to be able to make one that was of longer reach. He sent the one of 34 feet that is presently exposed on the terrace of the Observatory, where it was placed in the month of December 1672. . . . To be used in the meantime for testing, M. Campani has sent us four objectives of 80, 90, 100, and of 136 feet, which M. Colbert, prevented by his death, did not have time to test in the skies; the following year we were to discover even two more Satellites around Saturn that were closer than the others, and the revolutions of which were very much shorter.

This instrument provided even more stupefying results; in the same month, in fact, with it

Cassini had discovered the fifth satellite of Saturn in order of distance, which he named Rhea. She was the mythical wife of Saturn and mother of Jupiter, Neptune, and Pluto. Consequently, on Christmas Eve Cassini proudly reported to Louis XIV, having made his discovery of the new satellite by means of this instrument.

In a communication to Oldenburg in October 1673, Cassini was explaining how he had endeavored to observe the diameters of Jupiter’s satellites by means of the time of their immersion in Jupiter’s disk, measured by their passage across the face of the planet. “The diameter of the aperture in the object lens in the 35-foot telescope tube that we employ for the observations of Jupiter and Saturn is three inches paris inch” this gives a aperture about 81mm diameter ,,he wrote,“ whereas in the 21-foot telescope it is two and a quarter Paris inches is a aperture used between 62/64mm diameter or even something more, especially for Saturn. Actually, prefer we so much more this telescope of 35 feet which we have from Campani over the telescope of 36 feet which we have from Divini, that we use the former and lay the latter aside except when we have need of two telescopes of almost equal size and not very good quality.

The number 34 returns in the history of Cassini’s exploration of Saturn with a new and powerful telescope having a focal length of 34 ft, that is, more than 10 m. It had been commissioned by Colbert and King Louis XIV, and made, as usual, by Campani. This was the instrument that Cassini used to continue his observations of the planet and with which he discovered, on December 23, 1672, very close to Saturn, a third celestial body revolving around Saturn. Again, because of its position with respect to the planet, the astronomer called his second discovery “Intimus”, nowadays known as Rhea. The orbit of these two new satellites were described by Cassini in a volume published in 1673 with a fawning dedication to Louis XIV. Many colleagues criticized the obsequious “astronome mondaine” [socialite astronomer] Cassini, but it is also true that others acknowledged his availability and generosity.

This new generation telescope was so long that it could not be used from inside the observatory building, thus external structures like the wood tower shown on were set up to enable its use from the outside. This tower was called “the Marly”, because it had previously been used in Versailles as part of the so-called Machine de Marly to lift water for the reservoirs and fountains at the gardens, and now it was moved from there to the Observatory grounds to serve as a place for attaching the lenses of aerial telescopes.

Giuseppe Campani Objective #40, 137mm, 34 feet ( 11.9m F.L.) used at 76mm and 80mm diameter

Giuseppe Campani Objective #40, 137mm, 34 feet ( 11.9m F.L.)

Paris Observatory 17th century 34 foot telescope

Optical Test in OSLO of the 34 feet objective at different diameters

Colbert continued to request lenses from Campani that were yet larger, but it was not until 1681 that Campani succeeded in his endeavor to construct telescopes of a much greater focal length. For these he produced four lenses, which he offered to Colbert. One was of 100 palms focal length, another of 130, a third of 150, and the fourth of 200 palms. He was informed that the lenses had found acceptance with the Académie Royale des Sciences, and approved also at the same time was the method that Campani proposed for supporting long telescopes as well as the method for managing tubes of such great length that he had designed, and which he described and illustrated not long thereafter in a broadside he dedicated to Colbert, and which subsequently was illustrated by Bianchini in his work on Venus.

Cassini maintained that with Giuseppe’s objectives he had been able to make the first observations without the use of a tube, that is, he had made with aerial telescopes, and was able to do so with considerable facility. The method that had been proposed by Huygens, however, proved to be much more difficult for Cassini in practice. Together with his objectives, Campani exported various systems to serve them. An engraving of the period illustrated such a system in which are represented two telescopes to which have been applied mechanisms to facilitate terrestrial and celestial observations. The caption described:

Method of managing with facility Telescopes of any length, whether for Terrestrial as well as for Celestial [observations], invented in Rome by Gioseppe [sic] Campani, and applied in testing the four that he fabricated for the observatory of S.M.C.ma, the first of which is of 105 Roman palms, the second of 130, the third of 150 and the last of 205, dedicated to His Excellency, M. Colbert.

The tubeless telescope, which had been initiated by Huygens, eliminated the need for a supporting structure such as Campani had devised for testing his long lenses. Campani’s structure, dedicated to Minister Colbert, was illustrated in an engraving made in 1681 by the Accademia Fisico-matematica Romana (Academy of Physics and Mathematics in Rome) and subsequently republished by Bianchini. The test bed for terrestrial and celestial telescopes was rigged somewhat like a ship and allowed the observer to use the counterweight S to orient the heavy telescope almost by the touch of a finger. An inherent problem was that even a breeze could swing it out of alignment. The Accademia commissioned an elaborate scaffolding 79 feet (100 palms) long.

The French Academie approved a lesser contraption for a 100-foot telescope, requiring the manipulation of five heavy pulleys while observing. de Gottignies, Jesuit professor of the Collegio Romano, devised an improved version consisting of a 50-foot beam. Bianchini preferred Campani’s test bed, however, and he believed that a 50-foot telescope was required to view the spots of Jupiter, Saturn’s rings, and the planets, but to see all of the satellites of Saturn, a telescope of 100 feet was necessary.

Within a short time, a series of great discoveries were being made with Campani’s telescopes that confirmed all that had already been said about them. The most sensational of these was the discovery made in 1675 of the division of the ring of Saturn that was subsequently named “the Cassini division” in honor of the astronomer. While observing with a telescope equipped with a new objective of 100 palms that Giuseppe had sent to Paris, Cassini noted for the first time the obscure band that circled Saturn almost immediately below the equator. He fixed his attention above all to the ring, of which he magisterially described the structure, although none until then having been observed and then retained, “the breadth [width] of the ring is divided by a dark line in two equal parts, of which the inner, which is closer to the globe, appears very clear, and the external somewhat little dark.

From the colors of these two zones there was more or less the difference between raw or native silver and burnished silver. . . . The appearance of the ring is caused by a mass of very tiny satellites, having diverse movements that one of them can not be evaluated separately”. In March 1684, using the objective of 136 feet, Cassini discovered two more satellites of Saturn that were named Tethis and Dione. By this time, there was no longer any doubt about the excellence of the Campani instruments.

In March 1684, using the objective of 136 feet, Cassini discovered two more satellites of Saturn that were named Tethis and Dione. By this time, there was no longer any doubt about the excellence of the Campani instruments.

Since Minister Colbert had died unexpectedly in 1683, shortly after Cassini received the lenses and before Campani had been paid for them, the Marquis of Louvois, who succeeded Colbert, wished to close the account and wrote to Campani to inquire the price of the lenses. Recalling the generosity of Colbert with his previous order, and hoping for the same response from his successor, Campani hesitated to place an exact price on the work. In the meantime, the largest of the lenses—an exceptional objective of 205 palms (or 212 mm), had been accidentally broken in half while Cassini’s assistant was helping the astronomer manage the long tube. Louvois was then ordered by the widowed Queen Marie Therese to return the lenses to Campani and to pay him the amount of 3,000 scudi. Payment was delayed once more, however, due to the unexpected death of the French Queen in 1683, as we learn from a manuscript in Italian in the Biblioteca Vallicelliana of Rome, entitled “Order Given to Signor Campani by the Court of France''. Campani’s lens of 205 palms, mentioned in the foregoing, that had been split into two parts and subsequently had been repaired by Campani by applying mastic with great care, was not in fact the largest Campani lens that Cassini had used in Paris, for in the Observatory there is another signed by Campani that measures 49 meters of focal distance, corresponding to approximately 220 Roman palms, having a 22-cm aperture, and providing an enlargement of 600x.

Giuseppe Campani Objective #41 181mm diameter 40m F.L.

Objective lens at Paris Observatory #43 183mm diameter 48.5m F.L.

Paris Observatory objective lenses for aerial telescopes

This large lens that had been broken in half and glued together again, commissioned by Minister Colbert, was contained in a frame, and it end up in the Instituto delle Scienze of Bologna as a gift by pope Benedict XIV, together with Giuseppe’s workshop. That particular lens does not, however, appear to be the longest Campani objective used in France, for Abetti reported that the largest telescope used by Cassini is still preserved in the Paris Observatory. It bears the signature of Campani and measures approximately 49 meters of focal length, which corresponds to about 220 Roman palms, 22 cm of aperture, and furnishing an enlargement of 600x.

In the inventory made in 1793 of the instruments surviving in the Paris Observatory, which was published in 1810 by Cassini IV, more than 26 objectives by various makers were listed. At least one was signed by Campani, and bore the date 1672.1089 In his account of his life, Cassini wrote:

Campani continued to produce other telescopes even much longer, and he sent me three objectives of different sizes. Minister Colbert having unexpectedly died, Giuseppe requested the return of the lenses that he had sent me, in order to satisfy the Queen of Sweden. She also had planned my return to Rome, and wished to make an observatory in a building that was in the enclosure of the Palazzo Riario on the Lungara, where she lived. I did not have any intention to leave the service of the King, however, who provided me with benefits and was pleased with my services. It is why, with the permission of His Majesty, that I returned

to Campani the latest lenses of which the range is of an extraordinary length and inconvenient in use; it is in truth a task to make use of them, without any prince until now having desired them.

For the year 1687, the Comptes des Batiments noted, “For delivering: 4,000 livres to Signor Campani, in Rome for 4 large telescope lenses that he had sent in 1683, by order of the King, to serve the Observatory for astronomical observations. But it seems that these 4,000 livres were not to spare expense, the lenses were not paid for, and this was with the approval of Cassini, because they were too large, therefore too difficult to be used. On the basis of Gian Domenico Cassini’s statement, Cassini IV noted that the large objectives at the Observatory may not have been those of Campani, as one had believed, but those of Borelli, Huygens, and Hartsoeker.

Objective lens at Paris Observatory #42 239mm diameter 47.3m F.L.

Objective lens at Paris Observatory #44, 84mm diameter, 6.3m F.L.

Objective lens Inner diameter 6.7-5 cm , Outer diameter 10.7 cm 5m FL

Objective lens Inside diameter 4.7 cm , Outside diameter 6.9 cm 2m

Objective lens Inside diameter 5.3 cm , Outside diameter 7 cm

Objective lens Inside diameter 11.3 cm , Outside diameter 14 cm 2

Objective lens Inside diameter 7.7 cm , Outside diameter 10 cm

Objective lens Inside diameter 6.2 cm , Outside diameter 8.5 cm 4.5m FL

Objective lens Inside diameter 7.7 cm , Outside diameter 9.8 cm 5.9m FL

Objective lens Inside diameter 7.2 cm , Outside diameter 9.7 cm 5.6m FL

Objective lens Outside diameter 16.5 cm , Depth 0.6 cm lens 18m FL

Campani and Bianchini telescope relationship

The fame of Campani’s astronomical instruments that had reached England and in Europe earlier in his career was sustained to the last years of his life. In England, for example, his work was particularly highly esteemed. In discussing telescopes then being made in London, Robert Hooke, for example, noted that he had found some instruments equal in every way to those made by Campani, although much shorter in length. In Holland, Huygens had read with great interest notices concerning Campani’s instruments, and in a letter to Prince Leopold, he compared lenses made by common means with those that Campani had made on his lathe, as he claimed, working directly from the glass without molds. As previously noted, the French telescope maker Pierre Petit claimed that he would be able to make telescopic lenses equal to those of Campani if only he could have had access to the glass that Campani used; he never managed to do so, however.

Campani provided Bianchini with instruments for his observations, particularly those that the Monsignor used for the establishment of the meridian in the Church of Santa Maria degli Angeli. Among the instruments was a telescope of 50 palms focal length (1.17 meters) with which Bianchini reported he could discern a star of the first magnitude even in full daylight from inside the church while observing across the opposite openings in the wall.

For his observations, Bianchini also used a small telescope made by Campani of 1-1/2 palms (33 cm) with a reticule; for the most part, while observing within his house, he used a Campani telescope of focal length of 23 palms (5.13 meters). He constructed a meridian also in that lodging, which he described as being “in some of his rooms under Montecavallo. In the room in which I slept and where I studied”, he wrote, “I did not have to take more than two or three steps to make observations, having the position of the window at mid-day lined exact with the aperture in front of a garden, that left me free, and with sufficient space to accommodate telescopes of that length (23 palms) and even larger.

Upon being informed that Campani was engaged in developing a mechanical device for elevating aerial telescopes, with which he had been experimenting for the past 3 years, Bianchini was eager to participate, and he made arrangements for them to meet soon after his arrival in Rome.

The relationship between the two men, the savant Campani, now in middle age at 49, and the eager young scholar less than half his years, which had begun at first as colleagues engaged in mutual endeavors, had quickly developed into a close friendship.

Until now, even the most talented lens makers of the times had been unable to extend the focus of object lenses up to beyond barely 50 or 60 palms. Because the instruments then available proved to be inadequate, attempts at lunar observation eventually had to be abandoned. The difficulties in developing lenses to meet the required standards were so considerable that neither Divini nor Campani had as yet been able to produce telescopes of sufficient size capable of obtaining a clear vision of the patches on Venus.

The problem causing considerable difficulty in the construction of telescopes having greater focal length was derived from the instrument’s necessarily increased weight. Every attempt inevitably resulted in bending of the instrument a curve developing somewhere midway between the eyepiece and the objective. Although this particular problem had been anticipated early in the course of the process of raising the great telescopes skyward from a horizontal position, and a solution had constantly been sought, one that was entirely satisfactory had not yet been found.

The solution eventually was realized in a new invention—the “aerial telescope”, the use of telescopes without tubes. It appears to have been Minister Colbert who had provided the initial inspiration for experimenting with telescopes without tubes. This was confirmed in a document found among the Bianchini papers, which stated:

Doubting that because of the difficulty of raising [telescope] tubes there was such poor assurance of keeping them straight due to their extraordinary length, the Most Christian King generously arranged to have transported to the Observatory a great wooden tower [the tower of Marly]. Not deterring the astronomers from their work, on the other hand, this tower instead possibly could have many uses, and could be applied to still other important matters, such as for communicating some notices quickly to persons at great distances in times of war and in peace. [Meanwhile], a means had been studied of using only the lenses of the telescope without having need of the tube, in order to observe the objects of the sky; and of the earth, during the day as well as during the night. This had that advantage of clarity and distance that equaled, or at least perceptibly did not lessen, the latter.

It was Huygens who had been the first to attempt a means for developing the aerial telescope that ultimately provided a solution. In 1680, he experimented with the use of a narrow silk thread for directing the telescope’s lenses to the same distance of the foci despite the tube’s limitations. By means of this thread, the eyepiece and the object lens could be kept in perfect alignment with the object to be observed, with the axis being directed from the objective to the eyepiece, regardless of the elevation to be achieved, by utilizing a long thread between the ocular and object lenses to align them perfectly.

However, handling an aerial telescope was still not an easy task at all, and it seems that only Huygens and Cassini were able to get good results from them. The objective lens was mounted on a structure, as simple as a pole or a tree, or in a more complex manner such as the tower as in the case of the observatory of Paris, on a swivel ball-joint, while the observer stood on the ground and held the eyepiece which was connected to the objective by a string or a rigid rod; by holding the string tight and maneuvering the eyepiece, the observer could aim the telescope at objects in the sky. Actually, it was also because of the extreme difficulty of using these very long focal-length telescopes.

Anyway, Cassini made some personal modifications to improve the usability of this instrument. For example, he devised what he called a “tube à trois faces d’échelles” which is described in the book: “L’opera del genio italiano all’estero” by Savorgnan di Brazzà. Literally, the French expression means “three-sided ladder tube” and it was a sort of 20-m “tube” shaped as a triangular prism. Its wooden faces were not solid, but the rigidity of the structure was improved with respect to the standard rod thanks to a sort of “ladder-like” framework. The same arrangement included a mechanism that allowed the eyepiece to be moved back and forth along some grooves, and thus to set the focus with respect to the lens on the opposite side, which instead was fixed. Among other things, Giovanni Cassini elaborated a mount for spyglasses or telescopes with a clockwork system called “machine parallatique” or parallax machine that, similar to modern instrumentation, could compensate for the Earth’s rotation, so that one could fix a star in the sky and follow it for the whole night.

As Bianchini had related, Campani followed suit and developed the arrangement further. According to Bianchini, it had been Cassini who had urged Campani to attempt to construct telescopes of such great length in order to bring the focus of the objective lenses up to 100, 150, and even to 205 palms. In Bianchini’s view, it had been Colbert’s enthusiasm that had inspired Cassini, and Colbert’s enthusiasm in turn had derived from the resulting liberality of King Louis XIV, substantially reflected in the latest of the telescope lenses that Cassini received that Campani had sent to the Observatory in Paris in about 1682. Although Cassini meanwhile had managed to utilize these same lenses to discover four new satellites of Saturn that Huygens had not noticed in his observations of the planet, he had not managed to use the same lenses again after having undertaken and completed the method proposed by Huygens. Nonetheless, according to Bianchini, it was not until about 1712 that Cassini managed to make some last additions–the same year of his death–, which he brought to the attention of the Academie Royale. Cassini claimed that the method for making observations without tubes that had been proposed by Huygens was, in his experience, much more difficult in actual practice, and he noted further that it had been by using Campani’s lenses that he had been able to make the earliest observations with the greatest ease by means of the aerial telescope.

The mechanical arrangement that Campani invented made it possible to extend the length of an aerial telescope to almost 70 palms (15.63 m; 615,35 inches), by means of which an observer was enabled to view even the patches on the moon. Bianchini worked together with Campani, assisting him in erecting this telescope-elevating equipment in the Villa’s gardens. He described the event almost a half century later in Hesperis et Phosphori, in which he wrote: “in 1684, in the gardens of the Pamphilj outside the Janiculum gate, we saw the erection of Giuseppe Campani’s machine: thanks to it, for the first time the extension of the tube happily reached the length of almost 70 palms to observ the lunar spots”. The engraving was reproduced in Bianchini’s Hesperi et phosphori, from which it became widely known.

Campani telescope system depicted in Hesperis et Phosphori

Telescope design by Campani from New inventions of optical tubes of the accademia fisica matematica romana 1686

In Bianchini’s judgment, the method for using the aerial telescope proposed by Huygens resulted in being no more than ever inconvenient as far as the necessity to eliminate, at least in part, the foreign rays. The Dutch astronomer had been constrained, especially in observations of the craters of the moon, to surround the object lens with a sheet of cardboard that, as one could argue, served as a screen to every minimal breath of wind that created notable disturbance.

On the other hand, the method adopted by Cassini presented a notable improvement when compared with that of Huygens; the two movable frames with which the object lens had been furnished successfully facilitated the alignment of the eyepiece and object lens with the celestial object to be observed. The inconveniences, however, were not entirely eliminated if one considered that the external still somewhat disturbed the imagery and that the positioning of the object lens, even if it was facilitated by a small quadrant on which could be read the height of the star to be observed, had always to be entrusted to a second person.

It was the same Campani, Bianchini had noted in his manuscript, who had suggested to Cassini to place a small telescope close beside the object lens to further facilitate the work of the assistant. Bianchini attributed the concept of this idea entirely to Campani who, on the basis of this testimony, could consider himself the creator of that simple but precious application of the “seeker instrument” that, even to this day, remains extremely useful.

Early in the 1700s, Campani had constructed a telescope for use during his own

astronomical observations of such a notable size and having such power and clarity that from the convent of San Pietro in Montorio on the Gianicolo, using such a telescope of 30 palms, he was able to see the hand on the clock of the campanile of Frascati’s Duomo 11 miles distant. The superiority of the telescope without tubes, according to Bianchini, was undisputed, although Campani’s method did not in fact eliminate all the problems indicated. While the cords, if stretched taut, could eliminate the possibility that the long tube would curve, a problem remained of the difficulty of maneuvering or holding the instrument still without motion, given that its mass could not be of entirely overcome, even if they were stretched.

In making observations during succeeding years, both Campani and Bianchini continued to use telescopes without tubes. In 1712, Bianchini took with him from Rome to the royal observatory in Paris an apparatus for elevating aerial telescopes of 50 to 60 French feet (l foot = 32.48 cm) that subsequently was modified by the French for use with objectives of even greater focal length. This was the mechanism that had been devised by Campani in 1709, completed after an unknown number of years of experimentation.

Campani had attached a document to his reply to Marsili that was handwritten by Bianchini but unsigned, in which the Monsignor analyzed the subject of aerial telescopes. He expressed approval of Campani’s long focus telescopes but was opposed to those of Christiaan Huygens, he noted. Of particular interest in this document was Bianchini’s attribution to Campani of the idea of attaching a small telescope on the tube close to the object lens for the purpose of identifying celestial bodies.

The superiority of telescopes utilizing tubes over the aerial telescope, according to Bianchini, remained without question, although the method developed by Campani did not totally eliminate the problems indicated. While the ropes held well taut could eliminate curving of the long tube, the difficulty of maintaining or keeping the instrument immobile, given its massive structure, was not entirely surpassed if the same Campani and Bianchini made use of the telescope without tubes in the years that followed. In 1713, in fact, Bianchini presented to the Académie in France a new method for transporting and maneuvering large aerial telescopes.

Marsili felt that in Bianchini he had the perfect channel by means of which to obtain on his own behalf equitable precision in his orders. The judgments expressed by the young astronomer in favor of Campani was not sufficient with every probability, however, to overcome the obstacle of the high cost of the instruments. It was necessary to consider also that the long tubes constructed of wood, proposed by Campani, would have created serious problems of space in their use and storage in Marsili’s observatory. The larger telescopes certainly would have required that arrangements be made for their maintenance elsewhere.

The astronomical observatory in Berlin was founded officially on July 11, 1700, the Prince Elector’s birthday. Because the spendthrift Prince had provided only the most meager funding for it, the construction of the observatory consequently made slow progress. While waiting for the building to be completed, Kirch continued to make observations from his own home and from the private observatory of the wealthy amateur astronomer Baron von Krosigk.

Kirch noted that, on September 7, 1700, the Baron had acquired the Campani telescope from the Elector’s collection. According to his own account, Kirch used this instrument occasionally over a period of time. He was unable to make more frequent use of it, although he wished to do so, because he lacked the solid mounting required for supporting the long tube. Because of its length, it was difficult to manage the tube without one. In 1729, the Campani telescope at Berlin was being used also by his son, Christfried Kirch, who noted that its focal length was 16 feet, 11-1/2 inches– 516.89 cm.

In the observatory’s archives the instrument was described in the records as “A tube [telescope] with lenses made by Joseph Campani, having 3 ocular [lenses], with a focal length of 18 feet (518.16 cm), or when using a single eyepiece, a focal length of 16 feet–487.68 cm. The tube with a mounting is located at the balcony, the lenses are maintained in the room below”. Eventually the telescope was lost and has not been found.1260 The reputation for superiority of Campani’s instruments among astronomers in Germany continued even in his later years. Following the death in 1705 of Georg Christoph Eimmart, the Nuremberg astronomer, the senate of Nuremberg voted to acquire the entire contents of his private observatory and to construct a new installation at Altdorf. As the new observatory was nearing completion, efforts were made to equip it with the finest instruments available.

Berlin observatory in 1700

Among the Landgrave’s papers related to his visit to Campani’s shop during his sojourn in Italy was to be found a unique copy of Campani’s printed price list for his optical instruments, the only example that has come to light. On a sheet of paper was printed the measure of a Roman palm.

The remainder of the text in Italian is translated as follows:

Prices for Telescopes having four lenses of various lengths made by Giuseppe Campani in Rome, which he claims to be the most perfect that have been produced until now by any other Maker.

From 1-1/2 up to 2-1/2 palms valued at scudi – 20

From 3 palms up to 4-1/2 palms – 24

Of 6.37 palms – 30

Of 8 and 10 palms – 35

Of 12 and 13 palms – 45

Of 15 palms – 55

Of 20 palms – 75

Of 25 palms – 90

Of 30 palms – 120

Of 40 palms – 180

Of 60 palms – 300

Of 100 palms – 500

Of 150 palms – 800

Of 200 palms –1,000

Small Hand telescopes

Several of the Campani instruments that the Landgrave had purchased during that visit have survived and presently are preserved in the Museum für Astronomie und Technikgeschichte in Kassel. Among the Landgrave’s purchases while in Rome was a Campani screw-barrel microscope and a perspektiv or terrestrial telescope. Surviving is the large wooden telescope made by Campani in 1699, which the Landgrave had purchased during his visit to Campani’s shop and which he brought back to Kassel personally with him upon his return. Regrettably, its original mounting was destroyed during the bombing of Kassel in World War II.

Half a century later, Zacharias Conrad von Uffenbach, while touring through lower Saxony, Hesse, the Netherlands, and England, visited Kassel. There, on November 20, 1752, he was shown the Landgrave’s scientific collection by Professor Zumbach von Koesfeld. Uffenbach wrote an account of the visit, noting that: “After seeing some things that Zumbach had displayed for us, he shows us an ‘uncomparable’ object lens made by the most famous and finest glass cutter [sic, lens maker] whose name was inscribed on the periphery of the lens, ‘Giuseppe Campani in Roma 1684 Palmi 145’. It took 100 pistols of money because he—Campani—is very expensive and stubborn with his work”.

The story of this lens was told by an eyewitness, the French astronomer Joseph Jérôme Lefrançois de Lalande in an account of his travels in Italy in 1765 and 1766, during which he visited Bologna. While there he was taken by the curator, Ercole Lelli, on tour of the Institute of the Sciences. Lalande wrote, “M. Hercule Lelli, who exhibited them [the instruments in the Cabinet of Physics] showed me also an object-lens for a telescope having a focal length of 205 palms [141 French feet] the work of the celebrated Joseph Campani: it had been made by order of M. Colbert; but upon the death of this great Minister, which occurred in 1683, the lens was sent back to Rome: it had been broken into two pieces, but M. Campani rejoined the two pieces in such a manner that one could actually use it as if it were still whole, and this is the most beautiful telescope glass that exists in the world.

Giuseppe Campani Aerial telescope objective 180mm 32m FL at Kassel

Giuseppe Campani Aerial telescope eyepiece 50mm diam ( Kassel)

Giuseppe Campani Aerial telescope objective 180mm ( 111mm used) 32m FL at Kassel

Bellevue Kassel 1742 with Giuseppe Campani instruments

Aerial telescope mounting system made by Campani for the Kassel observatory

Giuseppe Campani telescope Kassel 9cm objective lens 4.5m

Museo Della Specola Bologna Giuseppe Campani Objective 13.8 cm, a focal length of 1210 cm

Museo Della Specola Bologna Giuseppe Campani Objective 75 mm diameter 4.1m FL, and behind 93 mmD. 8.20 m FL.

Museo Della Specola Bologna Giuseppe Campani Objectives: ( left to right) 137mm/12m F.L, 75mm/4.1m F.L. and 93mm/8.2m F.L. objective lenses

Among the instruments owned by Bianchini and which he had continued to use until late in his life was a telescope 50 palms (11.17 meters) in length which Campani had provided to him and with which it was possible to discern a star of the first size even in full daylight. In 1725, Bianchini observed the spots of Venus from the Platine, in a locality much adaptable for his use without disturbance, using a telescope of 90 palms (20.10 meters). By means of observations he made with aerial telescopes of 25 and 35 feet, made by Campani, Bianchini concluded that Venus rotates upon an axis inclined at approximately 75 degrees to the plane of its orbit in slightly more than 24 days.

This conclusion was quite in variance with the one obtained by Cassini. A critical comparison between the two sets of observations were made with telescopes of 82 and 114 feet focus, but they were unable to see any permanent markings on the disk. Campani no longer was able to work during the last several years of his life, and from the correspondence between Bianchini and Maraldi, it was apparent that it had become well known that lenses for telescopes now were available not from Campani but from his daughters.

Bianchini had continued to maintain contact with Campani even after his retirement. In a letter written in 1713, Marchese Paride Maria Salvago wrote to Bianchini: “I have heard with pleasure what you have said about Signor Campani, who does not wish to deprive the world of his secret method of working lenses. Having, as I am told, instructed his daughters, we shall have to see if they will know how to serve as has the father, and if they are furnished with the same ability and dexterity of hand.

In the same year, the Campani sisters furnished a telescope of 94 palms (21 meters) to the Count d’Osembray at the same time that they were busily involved with providing lenses and instruments that had been commissioned from their father for João V de Braganza, King of Portugal.

Giuseppe Campani died on July 28, 1715, at the age of 80 years. He was buried on the following day in his parish church of Santa Maria in Monterone. His death was noted in the records of the church preserved in the Vicariatio di Roma. Campani’s house in which he died was situated in the Piazza della Valle, formerly known as the Piazza dei Quatracci. It was adjacent to the Church of San Andrea della Valle and fronted upon the main doors of the convent of Sant’Andrea della Valle, which was attached at the left side of the church. Campani’s house was a free-standing building next to the church in the area now usurped by the Corso Vittorio Emanuele. He was a member of the parish of the nearby church of Santa Maria in Monterone, and it was for that reason that he was subsequently buried there.

TESTING CASSINI OBJECTIVE LENSES

Different simulations in OSLO using lenses diffraction limited using the same parameters has the objective lenses at Paris Observatory, all have a refractive index of 1.522 the same has the glass used by Campani and let's presume that all of these lenses are diffraction limited or near. Some of the objectives have a aperture mask to reduce the distortions near the egde of the lens and to limit chromatic aberrations, the chromatic index used is 1.5 at all the lenses.

Glass used is B270 window glass with a index of 1,522.