Richard Dunthorne
Encyclopedia
Richard Dunthorne was an English
astronomer
and surveyor, who worked in Cambridge as astronomical and scientific assistant to Roger Long
(master of Pembroke Hall and Lowndean Professor of Astronomy and Geometry), and also concurrently for many years as surveyor to the Bedford Level Corporation.
, where he attended the free grammar-school. There he attracted the notice of Roger Long
(later Master of Pembroke Hall, Cambridge), whose protégé Dunthorne became. Dunthorne moved to Cambridge where Long first appointed him as a "footboy", and where he received some further education (though this does not seem to have been regular university education). Dunthorne then "managed" a preparatory school in Coggeshall
, Essex
, and later returned to Cambridge where Long obtained for him an appointment as a "butler" at Pembroke Hall, an office that Dunthorne retained for the rest of his life. Here Dunthorne's main activity seems to have been in assisting Long in astronomical and scientific work.
Dunthorne also held an appointment for some years, concurrently with his work with Long, as superintendent of works of the Bedford Level Corporation, responsible for water management in the Fens
; he began this work several years" before 1761, continuing into the 1770s. In this role, Dunthorne was concerned in a survey of the fen
s in Cambridgeshire, and he also supervised construction of locks near Chesterton on the River Cam
.
Dunthorne's association with Long remained lifelong, and in the end Dunthorne acted as executor of Long's will.
lunar theory
of 1702, in order to facilitate testing Newton's theory.
In a 1746 letter to the keeper of Cambridge's Woodwardian Museum, Dunthorne wrote: "After I had compared a good Number of modern Observations made in different Situations of the Moon and of her Orbit in respect of the Sun, with the Newtonian Theory . . . I proceeded to examine the mean Motion of the Moon, of her Apogee, and Nodes, to see whether they were well represented by the Tables for any considerable Number of Years . . . "
On the basis of his observations, Dunthorne proposed some adjustments of the numerical terms of the theory.
in its orbit. Edmond Halley
in about 1695 had already suggested on the basis of comparison between contemporary observations and on the other hand ancient records for the timing of ancient eclipses, that the Moon was very gradually accelerating in its orbit. (It was not yet known in Halley's or in Dunthorne's time that what is actually happening is a slowing-down of the Earth's rate of rotation - see Ephemeris time
.) Dunthorne's computations, based in part on records of ancient accounts of eclipses, confirmed the apparent acceleration; and he was the first to quantify the effect, which he put at +10" (arcseconds/century^2) in terms of the difference of lunar longitude. Dunthorne's estimate is not far from those assessed later, e.g. in 1786 by de Lalande and still not very far away from the values from about 10" to nearly 13" being derived about a century later.
in 1761 and 1769,
and also published tables on the motion of Jupiter
's satellites in 1762.
(effectively led by Nevil Maskelyne
) appointed Dunthorne as the first "Comparer of the Ephemeris and Corrector of the Proofs" for the (then still future) Nautical Almanac and Astronomical Ephemeris
. The first issue appeared with data for the year 1767, breaking new ground in providing computational tools to enable mariners to use lunar observations to find their longitude at sea. Dunthorne worked as sole comparer for the first three issues, with data for 1767-69, and afterward continued as one of several comparers until the issue for 1776.
Dunthorne also contributed a method for clearing nautical lunar observations of the effects of refraction and parallax, for the purpose of finding the longitude at sea, and Maskelyne included this in his 'Tables requisite to be used with the Nautical Ephemeris', an accessory volume published to accompany the Nautical Almanac. It is also reported that Dunthorne in 1772 received from the Board of Longitude a reward of £50 for this contribution towards shortening the tedious calculations involved in "clearing the lunar distance" (at the same time as a similar reward was given to the contributor of an alternative method for the same purpose, Israel Lyons, 1739–1775). Improvements were added and "Dunthorne's improved method" was included in an edition of 1802.
In this area of celestial navigation, Dunthorne has been credited as the first to apply trigonometrical formulae for the general spherical triangle to the reduction of lunar distances and to give auxiliary tables for that purpose.
in 1765. The observatory was situated on the Shrewsbury Gate of St. John's College. Dunthorne also gave astronomical instruments to the College. The observatory remained in place until its closure in 1859.
A contemporary, Rev. William Ludlam (in charge of the St John's College observatory from 1767), described Dunthorne as one "who without the benefit of an Academical education is arrived at such a perfection in many branches of learning, and particularly in Astronomy, as would do honour to the proudest Professor in any University . . . he joined to a consummate excellence in his profession a generosity without limit in the exercise of it."
Dunthorne died at Cambridge. The crater Dunthorne
on the Moon is named after him.
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
astronomer
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
and surveyor, who worked in Cambridge as astronomical and scientific assistant to Roger Long
Roger Long
thumb|150px|Roger LongRoger Long was an English astronomer, and Master of Pembroke College, Cambridge between 1733 and 1770....
(master of Pembroke Hall and Lowndean Professor of Astronomy and Geometry), and also concurrently for many years as surveyor to the Bedford Level Corporation.
Life and work
There are short biographical notes of Dunthorne, one in the Philosophical Transactions (Abridgement Series, published 1809) (unsigned), another in the 'Dictionary of National Biography' (vol.16), and a third by W T Lynn. Dunthorne was born in humble circumstances in Ramsey, CambridgeshireRamsey, Cambridgeshire
Ramsey is a small Cambridgeshire market town and parish, north of Huntingdon and St Ives. For local government purposes it lies in the district of Huntingdonshire within the local government county of Cambridgeshire....
, where he attended the free grammar-school. There he attracted the notice of Roger Long
Roger Long
thumb|150px|Roger LongRoger Long was an English astronomer, and Master of Pembroke College, Cambridge between 1733 and 1770....
(later Master of Pembroke Hall, Cambridge), whose protégé Dunthorne became. Dunthorne moved to Cambridge where Long first appointed him as a "footboy", and where he received some further education (though this does not seem to have been regular university education). Dunthorne then "managed" a preparatory school in Coggeshall
Coggeshall
Coggeshall is a small market town of 3,919 residents in Essex, England, situated between Colchester and Braintree on the Roman road of Stane Street , and intersected by the River Blackwater. It is known for its almost 300 listed buildings and formerly extensive antique trade...
, Essex
Essex
Essex is a ceremonial and non-metropolitan county in the East region of England, and one of the home counties. It is located to the northeast of Greater London. It borders with Cambridgeshire and Suffolk to the north, Hertfordshire to the west, Kent to the South and London to the south west...
, and later returned to Cambridge where Long obtained for him an appointment as a "butler" at Pembroke Hall, an office that Dunthorne retained for the rest of his life. Here Dunthorne's main activity seems to have been in assisting Long in astronomical and scientific work.
Dunthorne also held an appointment for some years, concurrently with his work with Long, as superintendent of works of the Bedford Level Corporation, responsible for water management in the Fens
The Fens
The Fens, also known as the , are a naturally marshy region in eastern England. Most of the fens were drained several centuries ago, resulting in a flat, damp, low-lying agricultural region....
; he began this work several years" before 1761, continuing into the 1770s. In this role, Dunthorne was concerned in a survey of the fen
Fen
A fen is a type of wetland fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients...
s in Cambridgeshire, and he also supervised construction of locks near Chesterton on the River Cam
River Cam
The River Cam is a tributary of the River Great Ouse in the east of England. The two rivers join to the south of Ely at Pope's Corner. The Great Ouse connects the Cam to England's canal system and to the North Sea at King's Lynn...
.
Dunthorne's association with Long remained lifelong, and in the end Dunthorne acted as executor of Long's will.
Lunar tables
Dunthorne published a book of astronomical tables in 1739 entitled Practical Astronomy of the Moon: or, new Tables... Exactly constructed from Sir Isaac Newton's Theory, as published by Dr Gregory in his Astronomy, London & Oxford, 1739. These tables were modelled on Isaac Newton'sIsaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...
lunar theory
Lunar theory
Lunar theory attempts to account for the motions of the Moon. There are many irregularities in the Moon's motion, and many attempts have been made over a long history to account for them. After centuries of being heavily problematic, the lunar motions are nowadays modelled to a very high degree...
of 1702, in order to facilitate testing Newton's theory.
In a 1746 letter to the keeper of Cambridge's Woodwardian Museum, Dunthorne wrote: "After I had compared a good Number of modern Observations made in different Situations of the Moon and of her Orbit in respect of the Sun, with the Newtonian Theory . . . I proceeded to examine the mean Motion of the Moon, of her Apogee, and Nodes, to see whether they were well represented by the Tables for any considerable Number of Years . . . "
On the basis of his observations, Dunthorne proposed some adjustments of the numerical terms of the theory.
Acceleration of the Moon
Dunthorne is particularly remembered for his study of the phenomenon of the changing apparent speed of the MoonMoon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
in its orbit. Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...
in about 1695 had already suggested on the basis of comparison between contemporary observations and on the other hand ancient records for the timing of ancient eclipses, that the Moon was very gradually accelerating in its orbit. (It was not yet known in Halley's or in Dunthorne's time that what is actually happening is a slowing-down of the Earth's rate of rotation - see Ephemeris time
Ephemeris time
The term ephemeris time can in principle refer to time in connection with any astronomical ephemeris. In practice it has been used more specifically to refer to:...
.) Dunthorne's computations, based in part on records of ancient accounts of eclipses, confirmed the apparent acceleration; and he was the first to quantify the effect, which he put at +10" (arcseconds/century^2) in terms of the difference of lunar longitude. Dunthorne's estimate is not far from those assessed later, e.g. in 1786 by de Lalande and still not very far away from the values from about 10" to nearly 13" being derived about a century later.
Astronomical publications and observations
Dunthorne published papers in the Philosophical Transactions, including On the motion of the Moon (1746), On the acceleration of the Moon (1749), and the letter Concerning comets in 1751. He observed the transits of VenusVenus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
in 1761 and 1769,
and also published tables on the motion of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
's satellites in 1762.
Work for the Nautical Almanac
On 18 July 1765 the Board of LongitudeBoard of Longitude
The Board of Longitude was the popular name for the Commissioners for the Discovery of the Longitude at Sea. It was a British Government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.-Origins:Navigators and...
(effectively led by Nevil Maskelyne
Nevil Maskelyne
The Reverend Dr Nevil Maskelyne FRS was the fifth English Astronomer Royal. He held the office from 1765 to 1811.-Biography:...
) appointed Dunthorne as the first "Comparer of the Ephemeris and Corrector of the Proofs" for the (then still future) Nautical Almanac and Astronomical Ephemeris
The Nautical Almanac
The Nautical Almanac has been the familiar name for a series of official British almanacs published under various titles since the first issue of The Nautical Almanac and Astronomical Ephemeris, for 1767: this was the first nautical almanac ever to contain data dedicated to the convenient...
. The first issue appeared with data for the year 1767, breaking new ground in providing computational tools to enable mariners to use lunar observations to find their longitude at sea. Dunthorne worked as sole comparer for the first three issues, with data for 1767-69, and afterward continued as one of several comparers until the issue for 1776.
Dunthorne also contributed a method for clearing nautical lunar observations of the effects of refraction and parallax, for the purpose of finding the longitude at sea, and Maskelyne included this in his 'Tables requisite to be used with the Nautical Ephemeris', an accessory volume published to accompany the Nautical Almanac. It is also reported that Dunthorne in 1772 received from the Board of Longitude a reward of £50 for this contribution towards shortening the tedious calculations involved in "clearing the lunar distance" (at the same time as a similar reward was given to the contributor of an alternative method for the same purpose, Israel Lyons, 1739–1775). Improvements were added and "Dunthorne's improved method" was included in an edition of 1802.
In this area of celestial navigation, Dunthorne has been credited as the first to apply trigonometrical formulae for the general spherical triangle to the reduction of lunar distances and to give auxiliary tables for that purpose.
Benefactions in Cambridge
Dunthorne planned and funded the construction of an observatoryObservatory
An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed...
in 1765. The observatory was situated on the Shrewsbury Gate of St. John's College. Dunthorne also gave astronomical instruments to the College. The observatory remained in place until its closure in 1859.
A contemporary, Rev. William Ludlam (in charge of the St John's College observatory from 1767), described Dunthorne as one "who without the benefit of an Academical education is arrived at such a perfection in many branches of learning, and particularly in Astronomy, as would do honour to the proudest Professor in any University . . . he joined to a consummate excellence in his profession a generosity without limit in the exercise of it."
Dunthorne died at Cambridge. The crater Dunthorne
Dunthorne (crater)
Dunthorne is a small lunar impact crater that is located to the northwest of the small lunar mare called Palus Epidemiarum, in the southwest part of the Moon's near side. It lies to the southwest of the crater Campanus, and east of Vitello. Due south is Ramsden.This crater is roughly circular and...
on the Moon is named after him.
Dunthorne's publications
- Richard Dunthorne (1739), Practical Astronomy of the Moon: or, new Tables... Exactly constructed from Sir Isaac Newton's Theory, as published by Dr Gregory in his Astronomy, London & Oxford, 1739.
- Richard Dunthorne (1746), http://rstl.royalsocietypublishing.org/content/44/478-484/412.full.pdf"A Letter from Mr. Richard Dunthorne, to the Rev. Mr. Charles Mason, F. R. S. and Woodwardian Professor of Nat. Hist. at Cambridge, concerning the Moon's Motion", Philosophical Transactions, Volume 44 (1746), pp.412-420.
- Richard Dunthorne (1749), "A Letter from the Rev. Mr. Richard Dunthorne to the Reverend Mr. Richard Mason F. R. S. and Keeper of the Wood-Wardian Museum at Cambridge, concerning the Acceleration of the Moon", Philosophical Transactions (1683-1775), Vol. 46 (1749–1750) #492, pp. 162–172.
-- also given in Philosophical Transactions (abridgements) (1809), vol.9 (for 1744-49), p669-675 as "On the Acceleration of the Moon, by the Rev. Richard Dunthorne". - Richard Dunthorne (1751), "A Letter from Mr. Rich. Dunthorne to the Rev. Dr. Long, F. R. S. Master of Pembroke-Hall in Cambridge, and Lowndes's Professor of Astronomy and Geometry in That University, concerning Comets", Philosophical Transactions (1683-1775), Volume 47 (1751), pp. 281-288.
- Richard Dunthorne (1761), "Elements of New Tables of the Motions of Jupiter's Satellites: In a Letter to the Reverend Charles Mason, D. D. Woodwardian Professor in the University of Cambridge, and F. R. S. from Mr. Richard Dunthorne", Philosophical Transactions (1683-1775), Volume 52 (1761), pp. 105-107.
Other sources
- Mary Croarken (2002), "Providing Longitude for All", Journal of Maritime Research (National Maritime Museum, Greenwich), September 2002.
- Library of St John's College, Cambridge, (online article) mentioning Dunthorne in connection with his astronomically-related gifts to the college 1764-5, including a regulator clock by John Shelton.
- W T Lynn (1905), "Richard Dunthorne", The Observatory,vol.28 (1905), pp.215-6.
- Philosophical Transactions (Abridgement Series) (1809), vol.9 (for 1744-49) pages 669-70, (unsigned) biographical note about Richard Dunthorne.
- Frédéric Marguet (Capitaine de Vaisseau) (1931), "Histoire générale de la navigation du XVe au XXe siècle", Paris 1931, chapter 7, at page 242.
- Christof A. Plicht, "R. Dunthorne," Red Hill Observatory
- Curious About Astronomy
- "Right" Answers
- Maskelyne, N. (1767), Nautical Almanac and Astronomical Ephemeris, editions for 1767 and 1768; (see especially Maskelyne's Preface, acknowledging Dunthorne.