Solar eclipses observed at Greenwich during the time of Flamsteed & Halley (1675–1742)

 

page under construction

 

The intention of this page is to give details of all the solar eclipses observed from Greenwich while  Flamsteed and Halley held the post of Astronomer Royal.

John Flamsteed

John Flamsteed, the First Astronomer Royal. Line engraving by G. Vertue, 1721, after T. Gibson, 1712. Courtesy of the Wellcome Collection (see below)

During the whole time that the Observatory existed (1675-1998), there was only one total eclipse that could potentially be seen from the Observatory itself. This was the eclipse which occured while Flamsteed was Astronomer Royal in 1715.

 

Sources relating to Flamsteed's observations

As well as Flamsteed's manuscript observations (preserved at Cambridge), there are three main published sources of information:

Flamsteed corresponded in both English, Latin and other languages. In the published correspondence, if a letter wasn't written in English a translation has also been provided. Many of the letters can be read as part of a Google preview. A search of the correspondence for the word eclipse reveals that Flamsteed was a great collector of eclipse observations from the extensive network of astronomers he was in touch with at home and abroad.

Although Flamsteed shared his own observations with his correspondents, he was rather less inclined to put his observations into print prior to the publication of his Historia. Indeed, Willmoth has noted (in her introduction to the third volume of Correspondence) that after 1706, Flamsteed never voluntarily allowed his name to appear in the Transactions. There seem to be only four occasions when his solar eclipse observations were published in the Transactions. These were for the eclipses of 1676, 1687, 1706 & 1715. Of these, only those made during the eclipses of 1676 and 1706 were published in any detail. Those for the 1676 and 1687 eclipse were published in Latin, but were republished by the Society in English in an abridged form in the early 1800s. Where relevant, links to these are given below.

The story of how the Historiae Coelestis Libri Duo came to be published is complex and acrimonious and resulted in Flamsteed having a lifelong feud with both Edmond Halley and Isaac Newton. Funded originally by George Prince of Denmark, the consort of Queen Anne, and overseen by a committee of referees initially consisting of Newton, Christopher Wren, Dr John Arbuthnot, David Gregory and Francis Robartes, its printing began under the supervision of the bookseller Awnsham Churchill in May 1706, with the equivalent of 98 sheets (recorded by Flamsteed as 97 sheets) having been printed by December 1707. At this point, the press was stopped and following a dispute with the referees, Flamsteed was effectively cut out of the production process. Following the death of Prince George in 1708, production was funded by the Queen herself. Edited from this point onwards by Halley, the Historia was eventually published in 1712.

Following the death of both the Queen in 1714 and Newton’s patron, the Earl of Halifax, in 1715, Flamsteed was able to acquire 300 of the 400 copies that had been printed. After extracting only those pages that had been printed by the end of 1707 for reuse in an edition over which he had full control (the edition of 1725) , Flamsteed burnt the rest as a 'sacrifice to Truth' (Flamsteed Correspondence V3. p.789).

The so called pirated edition of the Historia published in 1712 contains measurements made by Flamsteed during solar eclipses up to the end of 1699. The 1725 contains those pages recycled from the 1712 edition only for those eclipses up to 1689. These appear in volume 1. The data for the 1693, 1694 and 1699 eclipses was printed afresh in a different format and published in volume 2. For these three eclipses, links to the relevant pages in both editions are given. For all the other eclipses, links are only given to the observations as they appear in the 1725 edition. Immediately after the Greenwich results for the eclipses up to 1689 Flamsteed also published the observations that had been sent to him by observers elsewhere.

For each of the eclipses, links are provided in the following order

  • Flamsteed's Historia Coelestis Britannica
  • Flamsteed's Historiae Coelestis Libri Duo (1693, 1694 & 1725 eclipses)
  • Philosophical Transactions (if any)
  • Correspondence (if any)
  • Eclipse Map (from Eclipsewise)

 

Where the observations were made

The first solar eclipse to occur after Flamsteed had been made Astronomer Royal occurred a few days before the Warrant was signed for the Building of the Observatory. If the weather had not been cloudy, Flamsteed would have observed the eclipse from the Tower of London where his Patron Jonas Moore had provided him with accommodation.

On 10 August 1675, Flamsteed had laid the Observatory's foundation stone and at about the same time moved from the Tower of London to the Queen's House at the bottom of Greenwich Park where he resided until the Observatory was in a state for him to move in. As the date of the 1676 eclipse approached, the building works were not quite finished and Flamsteed was still based in the Queen's House. However the Octagon Room was ready for occupation though and it was from here that this and all the subsequent were observed.

116915001

The Octagon Room as it appeared in Flamsteed's time. One of a series of etchings by Francis Place after Robert Thacker commissioned for Flamsteed c.1677–78. Key: (A) & (B) The two year going clocks with 2-second pendulums made by Thomas Tompion in 1676 and presented to Flamsteed by Sir Jonas Moore. (C) A further clock about which little is known. (D) 3-foot moveable quadrant at the opening on the northern side of the room (F) Stand for supporting the eye-end of a telescope tube with a screw mechanism for adjusting its height (S) Ladder for supporting the object-glass end of the tube. (T) Telescope tube (with square cross-section). In this image, there does not appear to be a micrometer attached. © The Trustees of the British Museum (CC BY-NC-SA 4.0). Museum number: 1865,0610.952 (see below)

Octagon Room plan c.1677 (Royal Observatory Greenwich)

Floor plan of the Octagon Room. North at the top. Etching (detail) by Francis Place after Robert Thacker c.1677–78 courtesy of Greenwich Heritage Centre.

As can be seen from the adjacent plan, the Octagon room had tall windows or glazed double doors onto balcony's on six of its eight sides. Whilst it is known for certain that the openings on the east and west side were windows, and those on the north, south-west and south-east were glazed doors, it is not certain of the opening on the south side was a window or a set of glazed doors (contemporary images vary in their depiction). It is clear from the image above, that the long telescope tubes used by Flamsteed could be positioned in front of both the east and the west windows. What is not clear however is whether they could be used at the openings with balconies. What is also unclear is if the ladder at the east window could be moved to other locations as required or if the room was fitted out with additional ladders.

 

Equipment used

Although all the eclipses after 1676 were timed by one of the  two year-going clocks by Tompion that can be seen in the image above. At the time of the 1676, they had still to be installed. Instead, Flamsteed used instead another clock that with a 1-second pendulum that had been made for him by Tompion the year before and was the clock Flamsteed subsequently used in the Sextant House. The errors of the clocks were found using the 3-foot moveable quadrant to measure the altitude of the sun.

To start with, the instruments used to view the eclipses was recorded alongside the observations in the Historias. However, no such information was given for those that occurred from 1706 onwards. In the Octagon Room, Flamsteed's instruments of choice seem to have been his 16 and 8-foot tubes each fitted with a micrometer. He used a projection screen (Scenam or Scænam) on at least six occasions. In a letter to Hill, dated 28 April 1715, discussing the 1715 eclipse, Flamsteed informed him that he observed it on a screen 'not being able in the 69th year of my age to stand to a telescope to view the Eclipse though it'.

Instrument
1675
1676
1684
1687
1689
1693
1694
1699
1706
1708
1715
1718
3-foot quadrant
23-foot tube
16-foot tube 1 3
? ? ?
8-foot tube 2 3 4
? ? ?
7-foot tube
projection screen

5
Tompion 2-sec pend
Tompion 1-sec pend
Moore's Clock ?

1   Also recorded as 196½-inches (16-foot 4½-inches) - the Telescopium Pedum Sedecin
2   Also recorded as 103½-inches (8-foot 7½-inches)
+   Used with a 3 foot glass in 1675 and a 7 foot tube in 1706 (phil trans)
3   Described as Tubo Brev and Tubo Long
4   Described as 'Tubo pedum, fere, 8' i.e. about 8-feet long
5   Information from correspondence
?   No telescopes specified in the Historia

 

A note on dates and times

Prior to 1752, rather than using the present Gregorian Calendar, the Julian Calendar was in use in Great Britain. For convenience, the dates shown in the headings below are the equivalent Gregorian dates.

The other thing to take into account is whether the the astronomers recorded their observations in terms of sidereal time as opposed to either local apparent solar time of local mean solar time.

It should also be noted that the astronomical day  began (at midday) twelve hours later than the civil day of the same date (which began at midnight).

 

The eclipse of 1675, June 23 (June 12)

Towneley Micrometer

The Towneley Micrometer. From volume 2 of Philosophical Transactions of the Royal Society of London in the library of the Natural history Museum Library, London. Downloaded from Internet Archive

This was the first solar eclipse to occur after Flamsteed became Astronomer Royal. Since the Royal Warrant for the building of the Observatory was not signed until a few days after this eclipse, Flamsteed's attempt to observe it would presumably have been made from the Tower of London where his Patron Jonas Moore had provided him with accommodation. In his letter to Towneley dated 8 June 1675, Flamsteed wrote of he preparations he was  making:

'Wee are here busy in prepareing for the Solar Eclipse   I am fitting up a three foot quadraant of my owne which I receaved lately out of the Country with a quicksilver level on the horizontall Radius and telescope sights of 3 foot: which I hope willl serve very well for Correcteing the clocks by. I intend to use two tubes. one of 23 the other of 7 foot with micrometers for determening the partes Eclipsed beginning and end, besides a 3 foot glasse to reaceave the species from it on a scene [a screen for receiving an image]. I doubt not but your are provides for it on Sunday morneing next, and that if the heavens blesse you with weather you will blesse us with your accurate observations' (Flamsteed Correspondence)

As things turned out, the weather was terrible as was explained by Flamsteed to Towneley in a further letter that he sent on 22 June after the eclipse:

'I am sorry to heare by yours of the 14th that your weather at Towneley was almost as ill as ours in London at the time of the eclipse. with us it was cloudy al night and the sun broke not forth next day till after noone. the cloudes came from the North which wee hoped might leave your heavens cleare: but the news of your letter has satified mee how vaine those hopes were and makes me feare my freinds in Derby shire who promissed to attend it had no better successe' (Flamsteed Correspondence)

 

The eclipse of 1676, June 11 (May 31 / 1 June)

This eclipse, which occurred in the morning of 1 June (old style), was an important occasion for the Observatory as not only was it the first celestial event that Flamsteed planned to observe there, but the King was also expected to be in attendance. At the start of the eclipse the Azimuth of the Sun was about 96o whilst at the end it was about 129o.

Sir-Jonas-Moore

Jonas Moore after an unknown artist. Frontispiece to Moore's Arithmetick (1660). Line engraving © National Portrait Gallery, London. Reproduced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported (CC BY-NC-ND 3.0) license (see below)

Fig.89 from Flamsteed's Historia

Fig.90 from Flamsteed's Historia

Fig.91 from Flamsteed's Historia

Figures 89, 90 & 91 from Flamsteed's Historia showing various stages of the eclipse. Engraved by John Senex and reproduced under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license courtesy ETH Zurich (see below)

On 10 August 1675, Flamsteed had laid the foundation stone at the Observatory and at about the same time had moved from the Tower of London to the Queen's House in Greenwich where he resided until the Observatory was in a state for him to move in. As the date of the eclipse approached, the building works were not quite finished and Flamsteed was still based in the Queen's House. However the Octagon Room was ready for occupation though at this point in time, the two year-going clocks (the Great Clocks) by Tompion had still to be installed.

In a letter to Towneley dated 27 May 1676 Flamsteed explained how he planned to prepare for the eclipse:

'I am now providing for the eclipse at which I intend to use a payre of tubes one of 16 the other of 8 foot for measuring the digits eclipsed and parts betwixt the cuspes. I hope you will doe the like. and be very carefull of your times in which I doubt not but I can be certaine to 10" seconds. I am now removeing my Astronomicall household stuffe from the Queens house to the Observatory where I have taken care to furnish my roome against the day of the Eclipse: at which the king intends to visit us and be present. Sir Jonas Moores Roome will also then be ready onley the house for the Sextant and wall Quadrant are not yet finished but will be in a short while.'

In the absence of the Great Clocks, Flamsteed set up the second-beating clock (the future Sextant House Clock) that had been made for him by Tompion the previous year and that he had been using while making observations from the Queen's House. Once installed at the Observatory, it was corrected from observations of the Sun made on 31 May, 1 June and 2 June (astronomical dates). Since the equation of natural days (the equation of time) had not been established at this point, the times given in the published observations are presumably the apparent time at Greenwich.

What Flamsteed did not tell Towneley was that Sir Jonas Moore was also going to be in attendance as was Lord Viscout Brouncker the President of the Royal Society. Nor did he tell him that Edmond Halley would be assisting him with the observations.

As things turned out, the King did not attend and Moore missed out as Flamsteed was to explain to Oldenburg in a letter dated 10 July:

'The most eminent Surveyor of the Ordnance [Jonas Moore] came down here on the previous day in order to witness the observation of this eclipse. But since from sunrise until seven o'clock in the morning the thickest clouds covered all parts of the heavens, he believed that there would be no clear sky and returned to London before the clouds began to part. Although they deprived us of the beginning together with all the phases after 8.40, they nevertheless permitted me to obtain the visible position and latitude of the moon well enough, though not to  discover its diameter accurately.' (Flamsteed Correspondence Vol 1, p.478-485)

He then went on to tell Oldenburg more about how the eclipse had been observed, much of which was repeated almost verbatim in his account that was later published in Philosophical Transactions:

'In conducting these observations, I was assisted by my friend Mr. Halley. We had prepared two tubes; the one 196½ inches long, having one of Townly’s micrometers, with which I took the measures of the first eight phases. The other was only 103½ inches long, with my own micrometer, and with which Mr. Halley took the observations. But in the last two observations, with this tube, (the micrometer of which is fitter for this use than the other) I took the distance of the azimuths falling by the sun’s lucid limb and the nearest cusp of the eclipse, while Mr. Halley in the mean time measured the lucid parts and the distance of the cusps, with the longer tube. A little before the beginning came Lord Viscount Brouncker, president of the Royal Society, who proved by his own judgment the measure of the sun’s diameter, taken with the longer tube. At 7h 45m the sun first appeared through the clouds.'

Flamsteed's Observations were published in different forms in five different publications. Confusingly, in the two Historias, the dates are given in terms of the Astronomical date. In the other three publications, they are given in terms of the civil date:

Publication
Comment
Flamsteed's letter to Oldenburg, 10 July 1676 (Flamsteed Correspondence Volume 1, p.478-485 Written in Latin, but with an English translation provided. Not viewable online. Includes a drawing of the eclipsed sun.
Mr. Flamstead's Letter, concerning his Observations, and those of Mr. Townley, and Mr. Halton of the late Eclipse of the Sun. Phil. Trans. R. Soc.11:662–667 (18 July 1676) Written in Latin. Does not include any drawings
Mr. Flamsteed's Letter, concerning his Observations, and those of Mr. Townley, and Mr. Halton of the late Eclipse of the Sun. (Phil Trans R, Soc, abridged, Vol 2 p.316-319 (1809) Abridged version of the above, but translated into English. Missing the obserations made to correct the clock
Observations as published in Historiae Coelestis Libri Duo p.199-202 [277-280] (1712)  Written in Latin. Identical to Historia Coelestis Britannica (below). Includes three drawings of the eclipsed Sun, p.204/5, fig. 89, 90 & 91
Observations as published in Historia Coelestis Britannica Volume 1 p.199-202 (1725) Written in Latin. Identical to Historia Coelestis Libri Duo (above), but quicker to download. Includes three drawing of the eclipsed Sun, p.204/5, figs. 89, 90 & 91

*Sources seem to differ as to when Flamsteed moved in. In the preface to his Historia of 1725 (Vol 3), Flamsteed states that he moved in August 1676. (Translation in NMM monograph No. 52 p113). In a letter to Edward Sherburne written on 12 July 1682, Flamsteed states that 'in Julye 1676 it was fit for habitation (See also Bailey p.126). Baily also quotes a memorandum of Flamsteed's in which Flamsteed supposedly says 'Entered it [the Observatory] in July 1676 (Bailey p.45). Birks (1999) states without quoting any sources that 'John Flamsteed moved into full occupation of the Royal Observatory on its completion on July 10th, 1676, three days after the installation of the "Great Clocks" [The Tompions] in the Octagon Room'. However, Flamsteed's Historia tells us that Flamsteed was still making observations from the Queen's House on 11 July, with the first published observation made at the Observatory being made on 26 September. An examination of  the catalogue of Flamsteed's papers, suggests that he continued making observations in the Queen's House until November 1676 (RGO1/13).

A later letter to Towneley dated 6 July 1676 (Flamsteed Correspondence) informs us:

' Wee shall have a payre of Watch clocks down here to morrow with pendulums of 13 foot and pallets partly after your manner. with which I hope wee may trie those experiments more accurately than with the second pendulum'.

 

The eclipse of 1684, July 12 (July 2 old style civil & astronomical)

This eclipse took place in the afternoon. It began at an azimuth of about 233o and ended at an azimuth of about 267o. In his The doctorine of the sphere, which was published in 1680, Flamsteed explained how to calulate the times of future eclipses. On p.58, he gave the timings for London (apparent time) of the 1684 eclipse, together with the number of digits that would be eclipsed.

Observations as published in Historia Coelestis Britannica Volume 1 p.324 (1725)

Eclipse Map (from Eclipsewise)

The doctrine of the Sphere. John Flamsteed (1680)

 

The eclipse of 1687, May 11 (May 1 old style civil & astronomical)

This minor partial eclipse took place in the afternoon. At the start of the eclipse the Azimuth of the Sun was about 211o whilst at the end it was about 228o.  Both the lucid parts and the cusps were measured together with the diameter of the Sun at the end of the eclipse. The end of the eclipse was also observed on a screen by Flamsteed's Assitant (Defiit Ministro supra Scenam). Observations made in Dorchester by D.Edwards were published in the Historia alongside Flamsteed's own observations. Mention of Flamsteed's Observations was also made in the Philosophical Transactions of the Royal Society and in various letters he wrote.

Observations as published in Historia Coelestis Britannica Volume 1 p.342 (1725)

Observations as published in Historiae Coelestis Libri Duo p.342 [424] (1712) 

Observationes nonnullæ Eclipseos Nuperæ Solaris … Phil. Trans. R. Soc.16:370–371 (31 Oct 1687)

English translation of above

Flamsteed also sent a copy of his observations in letter to Molyneux on 3 August 1687

Flamsteed also sent a copy of his observations in letter to Kirch on 17 October 1687

Writing to Newton on 27 April 1695, Flamsteed wrote:

'I have a solar Eclipse observed in May 1687 that will require a parallax less yet then your correction gives, by reason the Earth was then nearer the Aphelion,'

 

The eclipse of 1689, September 13 (September 3 old style civil and astronomical)

This minor eclipse took place in the afternoon. It began at an azimuth of about 241o and ended at an azimuth of about 255o.

Observations as published in Historia Coelestis Britannica Volume 1 p.350 (1725)

fig 136

Eclipse Map (from Eclipsewise)

 

1693 Jul 3 (June 23 old style civil and astronomical)

This minor eclipse took place in the afternoon. It began at an azimuth of about 184o and ended at an azimuth of about 210o. Although it was not observered at Greenwich, Halley included observations Flamsteed had received from Germany in the 1712 edition of the Historia.

Observations as published in Historia Coelestis Libri Duo p.56 [534] (1712)

Eclipse Map (from Eclipsewise)

 

1694 June 22 (June 12 old style)

This minor eclipse took place in the afternoon. It began at an azimuth of about 266o and ended at an azimuth of about 282o.

Observations as published in Historia Coelestis Libri Duo p.61 [539] (1712)

Observations as published in Historia Coelestis Britannica Volume 2 p.232 (1725)

Eclipse Map (from Eclipsewise)

 

The eclipse of 1699, September 23 (Sept 13 Old style civil, Sept 12 old style astronomical)

This eclipse took place in the morning. It began at an azimuth of about 116o and ended at an azimuth of about 153o suggesting that it was probably observed from the eastern window of the Octagon Room.

Observations as published in Historia Coelestis Libri Duo p.90 [568] (1712)

Observations as published in Historia Coelestis Britannica Volume 2 p.380 (1725)

Eclipse Map (from Eclipsewise)

In a letter to

 

The eclipse of 1700 September 13

Current tables state this was invisible from Greenwich and for 100s of miles around. Flamsteed seems to state that he saw the end of it at Greenwich. Correspondence 3 p.911. It seems that the eclipse he refers to was that of 13 September (Civil old style)

 

The eclipse of 1706, May 12 (May 1 old style civil, April 30 old style astronomical)

This eclipse took place in the morning. It began at an azimuth of about 107o and ended at an azimuth of about 145o. A detailed account (in English) was published in the Philosophical Transactions of the Royal Society (Vol. 25). For reasons that require further investigation, the figures given differ from those later published in the Historia. Both sets of figures also differ from those that Flamsteed sent Stanyan in a letter dated 24 May 1706.

Observations of the Solar Eclipse, May 1/12 1706. At the Royal Observatory at Greenwich, &c. John Flamsted. Phil. Trans. R. Soc.25:2237–2241 (1 June 1706)

Draft of letter from Flamsteed to Stanyan dated 24 May 1706

Observations as published in Historia Coelestis Britannica Volume 2 p.504 (1725)

Eclipse Map (from Eclipsewise)

 

The eclipse of 1708, September 14 (Sep 3 old style astronomical)

This eclipse took place in the morning. It began at an azimuth of about 96o and ended at an azimuth of about 119o. Flamsteed was at Burstow, where there were clear intervals only around mid-eclipse. Although this eclipse was also largely clouded out at Greenwich, wher the observations were made by James Hodgson. Hodgson's name was not recorded in the Historia, but it was recorded by Flamsteed in a letter to Abraham Sharp.

Observations as published in Historia Coelestis Britannica Volume 2 p.520 (1725)

Letter from Flamsteed to Abraham Sharp dated 14 September 1708

Eclipse Map (from Eclipsewise)

 

The total eclipse of 1715, May 3 (April 22 old style civil, April 21 old style astronomical)

The eclipse took place in the morning. It began at an azimuth of about 106o and ended at an azimuth of about 142o. It was the only total eclipse visible from the Observatory during the whole of its existence.

Observations as published in Historia Coelestis Britannica Volume 2 p.551 (1725)

Eclipse Map (from Eclipsewise)

Observations of the late total eclipse of the sun on the 22d of April last past, made before the Royal Society at their house in Crane Court in Fleet-street, London. By Dr. Edmund Halley, Reg. Soc. Secr. With an account of what has been communicated from aboard concerning the same. Phil. Trans. R. Soc.29:245–262 (31 May 1715)

Letter to Flamsteed to Hill dated 28 April stating that he observered it on a screen

Letter from Flamsteed to Abraham Sharp dated 11 October 1715 containing his observations

 

The eclipse of 1718, March 2 (Feb 19 old style civil. Feb 18 old style astronomical)

This eclipse took place in the morning. It began at sunrise with the eclipse already in progress at an azimuth of about 93o and ended at an azimuth of about 111o

Observations as published in Historia Coelestis Britannica Volume 2 p.563 (1725)

Eclipse Map (from Eclipsewise)

 

The eclipse of 1722, December 8

 

The total eclipse of 1724, May 22

This was a total eclipse in England, but not at Greenwich. It would appear that the weather across the whole country was unfavorable as there is only one known report of the eclipse having been observed.

 

Acknowledgements and Image licensing

The Towneley Mircometer

The 1721 image of John Flamsteed is reproduced in compressed form and at a reduced size courtesy of Wellcome Library, London (Public Domain Mark)

The images from the British Museum of the Octagon Room (Museum number: 1865,0610.952) is reproduced under an Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) license, courtesy of The Trustees of the British Museum. The Image has been cropped and resized for this website.

The portrait of Sir Jonas Moore after unknown artist. Line engraving, published 1660. © National Portrait Gallery, London. National Portrait Gallery Object ID: NPG D42258 is reproduced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported (CC BY-NC-ND 3.0) license.

The three diagrams of the eclipse of 1676 are reproduced under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license) license courtesy ETH Zurich and are taken from the 1712 edition of Flamsteed’s Historia (https://doi.org/10.3931/e-rara-79201).