# Hevelius-Hooke dispute

Johannes Hevelius of Danzig (1611-1687) was the most famous astronomer of his time, and also the last famous astronomer who did not use telescope. Most books on the history of astronomy (and even the Wikipedia article on Hevelius) mention a dispute between Hooke and Hevelius in which Hooke tried to convince him to use telescope. Now let me cite Rees's Cyclopedia or the universal dictionary (1819):

It is somewhat extraordinary that the dispute alluded to terminated with the public opinion in favor of plain sights, in preference to telescopic ones, as to the accuracy of observations made respectively with each...

In 1679, Dr. Halley traveled to Dantzic to settle the dispute between Dr. Hooke and Hevelius...

This dispute is always mentioned but without any detail. My question: what were the arguments of Hevelius against the telescopic sites?

Of course I understand that without a telescope you cannot see Jupiter satellites, phase of Venus, and other things discovered since Galileo. But here we are talking about "classical" astronomical observation, that is of measuring coordinates of stars and other celestial objects.

Reed refers to the book of Hevelius, Cometographia, I don't know whether it is available, and in any case, my Latin is not good enough to read it. Perhaps there exists some exposition of this discussion in a modern language?

Remark. I did a lot of this kind of observations myself, with marine sextants. And I can confirm that even a poor quality telescope helps. A sextant has a scale which can be read with 6" to 10" accuracy. With a naked eye I could measure the distance between two stars to 30" in the average (same accuracy as Hevelius). With a simple telescope 30x6 (without any micrometer) the accuracy is about 10"-15", almost the same as Hooke claimed. The difference is that Hevelius instruments were enormous, and the modern one is portable, and does not require a firm foundation.

As early as 1665 Oldenburg communicated Hooke's opinion that "few persons can distinguish an angle less than 1$'$", and that telescopic sights allow to make "instruments of much less bulk, to do ten times more". Hevelius replied in 1667 and asked for full description of telescopic sights fitted to sextants, and for inexpensive lenses of long focal length. But he also made his first arguments against the telescopic sights, and asked for a proof that telescopic sights are more accurate by comparing eight observations of angular distances between stars. Hooke never sent the lenses, despite being prompted to do so by the Royal Society, or took up Hevelius's challenge. The dispute escalated in 1673 after Hevelius gave an expanded version of his arguments in Machina Coelestis without mentioning Hooke.
Hevelius was an old school astronomer in the tradition of Tycho Brahe, he believed in using large instruments, including large telescopes, and "combining measurements from many instruments over a long period" to improve accuracy. In his 1674 pamphlet Animadversions Hooke didn't confine himself to rebutting Hevelius's arguments, but resorted to slights, implying that Hevelius's instruments were no better than Tycho's, and that he wasted his life when he could do so much better using telescopic sights. In this Hooke overestimated telescopic sights of his time, and underestimated Hevelius's instruments and skill. He achieved the accuracy of about 30$''$, whereas Flamsteed using telescopic sights only improved it to 15$''$-20$''$, hardly "ten times". When Halley was dispatched in 1679 to convert Hevelius to the use of telescopic sights his observations with a 2-foot quadrant did not prove superior to Hevelius's, who used 6 or even 9 feet quadrants with open sights. Only years after Hevelius’ death, when Flamsteed completed his new star catalog, did the advantage of telescopic sights become apparent.