The last great naked-eye astronomer.

Anybody cognizant with the history of astronomy in the Early Modern Period almost certainly thinks that the tittle of this post alludes to Tycho Brahe but in fact it refers to a man born ten years after the death of the great Danish astronomer. I am going to take a brief look at the life and work of Johannes Hevelius who was born on 28^th January 1611 in Danzig (Gdansk) where he also died seventy-six years later on 28^th January 1687. Like most people who lived in this period and particularly those living in the areas claimed historically by both Poland and Germany his real name is disputed, Hevelius being of course a Latinised nom de plum. His nationality is also hotly discussed by those who cannot accept that modern concepts of nationality are not really applicable to seventeenth century Europe. What is not disputed is that he was the child of a wealthy Germany speaking bier-brewing dynasty, although his parents sent him away as a child to learn Polish. Now it might at first seem strange to call a man notorious for his spectacular self constructed telescopes (of which more later) the last great naked-eye astronomer but this appellation is justified and why it is so is the main purpose of this post.

Johannes Hevelius by Daniel Schultz

Hevelius attended the local grammar school in Danzig where he had the good fortune to receive tuition from Peter Crüger. Crüger a graduate of the University of Wittenberg was a significant astronomer in his own right and was the professor for mathematics and poetics at the school. He not only taught the young Hevelius the elements of mathematics and astronomy but also instructed him in the construction of astronomical instruments and the art of engraving. Hevelius proved a willing and very able pupil.

Leaving school Hevelius went on to study law at Leiden in Holland then one of the leading European universities. After his studies he went on a tour of Europe meeting and becoming friends with many of the leading astronomers and mathematicians of the age. Returning to Danzig he took over the family business, which he directed with great financial success, and married Katherine Rebschke who would inherit the two houses neighbouring the brewery. Later after the death of his father Hevelius would erect a large observatory on the roofs of the three houses, which became something of a tourist attraction in Danzig. Hevelius was very engaged in communal politics serving as a town councillor and even for a time as mayor. However his real life-long passion was astronomy to which he dedicated an immense amount of time, energy and money.

Hevelius designed and constructed his own instruments and telescopes with longer and longer focal lengths in an attempt to reduce spherical aberration.

Realising that the construction of such long tubes created problems of stability Hevelius went on like Huygens to construct tubeless aerial telescopes creating a monster with a focal length of forty-five metres (150 feet). Large crowds would assemble to watch this monster being steered across the night sky.

Hevelius devoted several years to mapping the moon culminating in the publication of his Selenographia in 1647. As well as containing the most accurate and detailed maps of the moon made up to that time the book also displayed others aspects of Hevelius’ extraordinary skills. Hevelius was not only responsible for all of the observations but had produced all of the drawings himself as well as making the engravings from which the drawings were printed. Hevelius believed that only by carrying out all stages of the process himself could he guarantee the exclusion of mistakes.

In 1662 his wife Katherine died and Hevelius married Elizabeth Koopmann the following year who was at the time only sixteen years old. Unlike his first wife Elizabeth was also passionately interested in astronomy and became Hevelius’ assistant in the observatory. After his death she would go on to edit and publish their jointly compiled star catalogue making her one of the earliest female astronomers.

Johannes and Elizabeth observing together

By the 1670s Hevelius was recognised as the leading European observational astronomer when he published his Machina coelestis a detailed description of his astronomical instruments in 1673. This book led to a major scientific controversy that revolves around the claim contained in the tittle of this post.

By this point in the development of astronomical instruments most observational astronomers were using instruments fitted with telescopic sights containing cross hairs to increase the accuracy of the measurements made. Hevelius, however, was still using instrument fitted with simply non-telescopic open sights relying on naked-eye observations. When Robert Hooke in London read of Hevelius’ decision not to employ telescopic sights and to rely instead on naked-eye observations he publicly denounced Hevelius’ work as valueless. He also attacked Hevelius’ methods of graduating and marking the circular scales on his instruments calling them old fashioned and inaccurate at the same time naturally praising his own superior methods. Hooke was however not criticising a naïve beginner or shy amateur. Hevelius was a wealthy businessman, a successful politician in a major European city and one of the leading European astronomers he reacted. He was an honoured foreign member of the Royal Society, Hooke’s employers, and he now turned to this august institution and complained about Hooke’s insulting behaviour and requesting them to send one of their members to Danzig to confirm the accuracy of his work. The Royal Society was in somewhat of a quandary. On the one side Hevelius had a very high status in the European scientific community of the time on the other side Hooke’s criticisms had, at least theoretically, a certain justification.

In 1679 the young Edmund Halley paid a visit to Hevelius in Danzig bringing with him the quadrant with telescopic sights that he had used on St Helena to map the southern skies in 1676-77. The two men carried out a series of extensive observations and measurements using Hevelius’ instruments and Halley’s quadrant at the end of which Halley confirmed that Hevelius’ naked-eye observations were just as accurate as his own telescopic ones. Hevelius had proved that he was truly a first class observer

Shortly after Halley’s visit Hevelius’ brewery and observatory together with all of his books, papers and instruments were destroyed in a fire that was probably laid on purpose. Hevelius was now sixty-nine years old and a lesser man would probably have given up but Hevelius was made of sterner stuff. With the help of friends and patrons he succeeded in rebuilding his observatory and his equipment and to take up his work again which he continued until his death seven years later.

Although he had vindicated himself in his observational trial with Halley in reality Hooke was right and Hevelius’ methods were out dated and he would go down in history as the last great naked-eye astronomer.

Last year there was a major academic conference in Danzig to celebrate the four-hundredth anniversary of Hevelius’ birth and a major international research project has been started to edit and publish his very extensive scientific correspondence so we can expect to hear more of the bier brewing star gazer of Danzig in the next few years.