William Herschel#Herschel's telescopes

Herschel was born in the Electorate of Hanover in Germany, then part of the Holy Roman Empire, one of ten children of Isaak Herschel and his wife, Anna Ilse Moritzen, of German Lutheran ancestry. His ancestors came from Pirna, in Saxony. Theories that they were Protestants from Bohemia have been questioned by Hamel as the surname Herschel already occurred a century earlier in the very same area in which the family lived.

Herschel's father was an oboist in the Hanover Military Band. In 1755 the Hanoverian Guards regiment, in whose band Wilhelm and his brother Jakob were engaged as oboists, was ordered to England. At the time the crowns of Great Britain and Hanover were united under King George II. As the threat of war with France loomed, the Hanoverian Guards were recalled from England to defend Hanover.

After they were defeated at the Battle of Hastenbeck, Herschel's father Isaak sent his two sons to seek refuge in England in late 1757. Although his older brother Jakob had received his dismissal from the Hanoverian Guards, Wilhelm was accused of desertion{{cite journal |last=Hoskin |first=M. |journal=Journal for the History of Astronomy |title=Was William Herschel a deserter? |bibcode=2004JHA....35..356H |volume=35, Part 3 |issue=120 |pages=356–358 |date=2004|doi=10.1177/002182860403500307 |s2cid=117464495 }} (for which he was pardoned by George III in 1782).{{Gutenberg book|bullet=none|last=Clerke|first=Agnes M.|author-link=Agnes Mary Clerke|name=A Popular History of Astronomy During the Nineteenth Century|place=London (republished eText) |publisher=Adam and Charles Black|date=1908|edition=4th|page=18|no=28247}}

Wilhelm, nineteen years old at this time, was a quick student of the English language. In England, he went by the English rendition of his name, Frederick William Herschel.

In addition to the oboe, he played the violin and harpsichord and later the organ.{{sfn |Holmes |2008 |p=67}} He composed numerous musical works, including 24 symphonies and many concertos, as well as some church music.{{cite web |last1=Griffiths |first1=Martin |title=Music(ian) of the spheres William Herschel and the astronomical revolution |date= 18 October 2009 |url=http://www.lablit.com/article/550 |website=LabLit |access-date=4 June 2018}}

Six of his symphonies were recorded in April 2002 by the London Mozart Players, conducted by Matthias Bamert (Chandos 10048).{{cite web |title=Chan 10048 William Herschel (1738–1822) |url=https://www.chandos.net/products/catalogue/CHAN%2010048 |website=Chandos |access-date=4 June 2018}}

File:William Herschel - Symphony No. 15 - British Library Add MS 49626 f25r.jpg

He was head of the Durham Militia band from 1760 to 1761.{{cite web |date=24 May 2017 |title=Seagull city: Sunderland's literary and cultural heritage |url=https://wp.sunderland.ac.uk/seagullcity/sir-william-herschel/ |website=Seagull city}} Herschel moved to Sunderland in 1761; Charles Avison engaged him as the first violin and soloist for his Newcastle orchestra, where he played for one season. In "Sunderland in the County of Durh: apprill {{sic}} 20th 1761" he wrote his Symphony No. 8 in C Minor. He visited the home of Sir Ralph Milbanke at Halnaby Hall near Darlington in 1760,{{cite book |last=Lubbock |first=Constance Ann |title=The Herschel Chronicle: The Life-story of William Herschel and His Sister, Caroline Herschel |url=https://books.google.com/books?id=Hcc5AAAAIAAJ&pg=PA1 |date=1933 |publisher=CUP Archive |pages=1–}}{{rp|14}} where he wrote two symphonies, as well as giving performances himself.

After Newcastle, he moved to Leeds and Halifax where he was the first organist at St John the Baptist church (now Halifax Minster).{{cite book |first=John C. |last=Barentine |title=The Lost Constellations: A History of Obsolete, Extinct, or Forgotten Star Lore |publisher=Springer |year=2015 |page=410 |url=https://books.google.com/books?id=u_7NCgAAQBAJ&pg=PA410|isbn=978-3319227955 }}{{rp|411}}

In 1766, Herschel became organist of the Octagon Chapel, Bath, a fashionable chapel in a well-known spa, in which city he was also Director of Public Concerts.{{cite book |editor-last1=Cowgill |editor-first1=Rachel |editor-last2=Holman |editor-first2=Peter |title=Music in the British Provinces, 1690–1914 |date=2007 |publisher=Routledge |location=London and New York |isbn=978-1351557313 |pages=100–111 |url=https://books.google.com/books?id=tTkrDwAAQBAJ&pg=PA100 |access-date=4 June 2018}} He was appointed as the organist in 1766 and gave his introductory concert on 1 January 1767. As the organ was still incomplete, he showed off his versatility by performing his own compositions including a violin concerto, an oboe concerto, and a harpsichord sonata.{{cite journal |last1=Duckles |first1=V. |title=Sir William Herschel as a Composer |journal=Publications of the Astronomical Society of the Pacific |date=1962 |volume=74 |issue=436 |pages=55–59 |bibcode=1962PASP...74...55D |doi=10.1086/127756 |doi-access=free }}

On 4 October 1767, he performed on the organ for the official opening of the Octagon Chapel.{{cite book |last1=Macpherson |first1=Hector Copland |title=Herschel |date=1919 |publisher=Society for Promoting Christian Knowledge; Macmillan |location=London & New York |page=13 |url=https://books.google.com/books?id=sWEtAQAAMAAJ&pg=PA13 |access-date=4 June 2018}}

His sister Caroline arrived in England on 24 August 1772 to live with William in New King Street, Bath.{{rp|1–25}} The house they shared is now the location of the Herschel Museum of Astronomy.{{cite web |title=Welcome to Herschel Museum of Astronomy |url=http://herschelmuseum.org.uk/ |website=Herschel Museum of Astronomy |access-date=4 June 2018}} Herschel's brothers Dietrich (1755–1827), Alexander (1745–1821) and Jakob (1734–1792) also appeared as musicians of Bath.{{citation | title=Alexander Herschel: The forgotten partner| last1=Hoskin | first1=M.| journal=Journal for the History of Astronomy|volume=35 | number=4 | pages=387–420 | year=1980 | bibcode=1980JHA....11..153H | postscript=. | doi=10.1177/002182868001100301| s2cid=115478560 }} In 1780, Herschel was appointed director of the Bath orchestra, with his sister often appearing as soprano soloist.{{cite book |last1=Schaarwächter |first1=Jürgen |title=Two Centuries of British Symphonism: From the beginnings to 1945 |date=2015 |publisher=Verlag |location=Olms |isbn=978-3487152288 |url=https://books.google.com/books?id=EIvoCQAAQBAJ&pg=PA67 |access-date=4 June 2018}}

File:HerschelTelescope.jpg, Bath, of a telescope similar to that with which Herschel discovered Uranus]]

File:William Herschel's Mirror-polisher.jpg, London]]

Herschel's reading in natural philosophy during the 1770s not only indicates his personal interests, but also suggests an intention to be upwardly mobile, both socially and professionally. He was well-positioned to engage with eighteenth-century "philosophical gentlemen" or philomaths, of wide-ranging logical and practical tastes.{{cite journal |last1=Winterburn |first1=E. |title=Philomaths, Herschel, and the myth of the self-taught man |journal=Notes and Records |date=25 June 2014 |volume=68 |issue=3 |pages=207–225 |doi=10.1098/rsnr.2014.0027 |pmid=25254276 |pmc=4123665 }}

Herschel's intellectual curiosity and interest in music eventually led him to astronomy. After reading Robert Smith's Harmonics, or the Philosophy of Musical Sounds (1749), he took up Smith's A Compleat System of Opticks (1738), which described techniques of telescope construction.{{cite web |title=Sir William Herschel British-German astronomer |url=https://www.britannica.com/biography/William-Herschel |website=Encyclopaedia Britannica |access-date=4 June 2018}} He also read James Ferguson's Astronomy explained upon Sir Isaac Newton's principles and made easy to those who have not studied mathematics (1756) and William Emerson's The elements of trigonometry (1749), The elements of optics (1768) and The principles of mechanics (1754).

Herschel took lessons from a local mirror-builder and having obtained both tools and a level of expertise, started building his own reflecting telescopes. He would spend up to 16 hours a day grinding and polishing the speculum metal primary mirrors. He relied on the assistance of other family members, particularly his sister Caroline and his brother Alexander, a skilled mechanical craftsperson.

He "began to look at the planets and the stars"{{cite book|last=Levy|first=David H.|title=The Quest for Comets An Explosive Trail of Beauty and Danger|date=1994|publisher=Springer US|location=Boston|isbn=978-1489959980|page=38|url=https://books.google.com/books?id=6F_5BwAAQBAJ&pg=PA38|access-date=17 May 2018}} in May 1773 and on 1 March 1774 began an astronomical journal by noting his observations of Saturn's rings and the Great Orion Nebula (M42).

The English Astronomer Royal Nevil Maskelyne visited the Herschels while they were at Walcot (which they left on 29 September 1777).{{cite book |last1=Hoskin |first1=Michael |title=The construction of the heavens : the cosmology of William Herschel |date=2012 |publisher=Cambridge University Press |location=Cambridge |isbn=978-1107018389 |page=77 |url=https://books.google.com/books?id=Wk4b88e-qKYC&pg=PA77 |access-date=6 June 2018}}

By 1779, Herschel had also made the acquaintance of Sir William Watson, who invited him to join the Bath Philosophical Society. Herschel became an active member, and through Watson would greatly enlarge his circle of contacts.{{cite journal |last1=Ring |first1=Francis |title=The Bath Philosophical Society and its influence on William Herschel's career |journal=Culture and Cosmos |date=2012 |volume=16 |pages=45–42 |doi=10.46472/CC.01216.0211 |url=http://www.cultureandcosmos.org/pdfs/16/Ring_INSAPVII_William_Herschel.pdf |access-date=4 June 2018|doi-access=free }} A few years later, in 1785, Herschel was elected an international member of the American Philosophical Society in Philadelphia.{{Cite web|title=APS Member History|url=https://search.amphilsoc.org/memhist/search?creator=william+herschel&title=&subject=&subdiv=&mem=&year=&year-max=&dead=&keyword=&smode=advanced|access-date=14 December 2020|website=search.amphilsoc.org}}

Herschel's early observational work soon focused on the search for pairs of stars that were very close together visually. Astronomers of the era expected that changes over time in the apparent separation and relative location of these stars would provide evidence for both the proper motion of stars and, by means of parallax shifts in their separation, for the distance of stars from the Earth. The latter was a method first suggested by Galileo Galilei.{{cite book|last=Aitken|first=Robert Grant|title=The Binary Stars|date=1935|publisher=McGraw-Hill Book Company, Inc.|location=New York and London|isbn=978-1117504094 |pages=4–9|url=https://archive.org/stream/binarystars00aitk#page/4/mode/2up}}

From the back garden of his house in New King Street, Bath, and using a {{convert|6.2|in|mm|adj=mid|aperture}}, {{convert|7|ft|m|adj=mid|-focal-length}} (f/13) Newtonian telescope "with a most capital speculum" of his own manufacture,{{harvnb|Mullaney|2007|p=10}} in October 1779, Herschel began a systematic search for such stars among "every star in the Heavens",{{rp|5}} with new discoveries listed through 1792. He soon discovered many more binary and multiple stars than expected, and compiled them with careful measurements of their relative positions in two catalogues presented to the Royal Society in London in 1782 (269 double or multiple systems){{cite journal|last1=Herschel|first1=Mr. |last2=Watson |first2=Dr. |title=Catalogue of Double Stars. By Mr. Herschel, F.R.S. Communicated by Dr. Watson, Jun |journal=Philosophical Transactions of the Royal Society of London |date=1 January 1782 |volume=72 |pages=112–162 |doi=10.1098/rstl.1782.0014 |bibcode=1782RSPT...72..112H |quote=Read January 10, 1782|doi-access=free}} and 1784 (434 systems).{{cite journal |last1=Herschel |first1=W. |title=Catalogue of Double Stars. By William Herschel, Esq. F.R.S |journal=Philosophical Transactions of the Royal Society of London |date=1 January 1785 |volume=75 |quote=Read December 8, 1784 |pages=40–126 |doi=10.1098/rstl.1785.0006 |bibcode=1785RSPT...75...40H |s2cid=186209747}} A third catalogue of discoveries made after 1783 was published in 1821 (145 systems).{{cite journal |last1=Herschel |first1=W. |title=On the places of 145 new Double Stars |journal=Memoirs of the Royal Astronomical Society |date=1821 |volume=1 |page=166 |quote=Read June 8, 1821|bibcode=1822MmRAS...1..166H }}{{cite web |last1=MacEvoy |first1=Bruce |title=The William Herschel Double Star Catalogs Restored |url=http://www.handprint.com/ASTRO/herschel.html |website=Astronomical Files from Black Oak Observatory |access-date=5 June 2018}}

The Rev. John Michell of Thornhill published work in 1767 on the distribution of double stars,{{cite book |last1=Heintz |first1=Wulff D. |title=Double stars |date=1978 |publisher=Reidel |location=Dordrecht |isbn=978-9027708854 |page=4 |url=https://books.google.com/books?id=6-PqCAAAQBAJ&pg=PA4 |access-date=4 June 2018}} and in 1783 on "dark stars", that may have influenced Herschel.{{cite journal |last1=Schaffer |first1=Simon |title=John Mitchell and Black Holes |journal=Journal for the History of Astronomy |date=1979 |volume=10 |pages=42–43 |url=http://adsbit.harvard.edu//full/1979JHA....10...42S/0000042.000.html |access-date=4 June 2018|bibcode=1979JHA....10...42S |doi=10.1177/002182867901000104 |s2cid=123958527 }} After Michell's death in 1793, Herschel bought a ten-foot-long, 30-inch reflecting telescope from Michell's estate.{{cite book |last1=Geikie |first1=Archibald |title=Memoir of John Michell |date=2014 |publisher=Cambridge University Press |isbn=978-1107623781 |pages=12–18, 95–96 |url=https://books.google.com/books?id=-VFkAgAAQBAJ |access-date=4 June 2018}}

In 1797, Herschel measured many of the systems again, and discovered changes in their relative positions that could not be attributed to the parallax caused by the Earth's orbit. He waited until 1802 (in Catalogue of 500 new Nebulae, nebulous Stars, planetary Nebulae, and Clusters of Stars; with Remarks on the Construction of the Heavens) to announce the hypothesis that the two stars were "binary sidereal systems" orbiting under mutual gravitational attraction, a hypothesis he confirmed in 1803 in his Account of the Changes that have happened, during the last Twenty-five Years, in the relative Situation of Double-stars; with an Investigation of the Cause to which they are owing.{{rp|8–9}} In all, Herschel discovered over 800 confirmed[http://www.handprint.com/ASTRO/Herschel_All.html William Herschel's Double Star Catalog]. Handprint.com (5 January 2011). Retrieved on 5 June 2011. double or multiple star systems, almost all of them physical rather than optical pairs. His theoretical and observational work provided the foundation for modern binary star astronomy;{{rp|74}} new catalogues adding to his work were not published until after 1820 by Friedrich Wilhelm Struve, James South and John Herschel.{{cite book |last1=North |first1=John |title=Cosmos : an illustrated history of astronomy and cosmology |date=2008 |publisher=Univ. of Chicago Press |location=Chicago |isbn=978-0226594415 |url=https://books.google.com/books?id=qq8Luhs7rTUC&pg=PA448 |access-date=5 June 2018}}{{cite book |last1=Cavin |first1=Jerry D. |title=The Amateur Astronomer's Guide to the Deep-sky Catalogs |date=2011 |publisher=Springer Verlag |location=New York |isbn=978-1-4614-0655-6 |url=https://books.google.com/books?id=obLAoHOVodAC&pg=PA148 |access-date=5 June 2018}}

{{main|Uranus#History}}

File:Uranus Voyager2 color calibrated.png, discovered by Herschel in 1781]]

In March 1781, during his search for double stars, Herschel noticed an object appearing as a disk. Herschel originally thought it was a comet or a stellar disc, which he believed he might actually resolve.{{sfn |Holmes |2008 |p=96}} He reported the sighting to Nevil Maskelyne the Astronomer Royal.{{cite book |last1=Raffael |first1=Michael |title=Bath Curiosities |date=2006 |publisher=Birlinn |isbn=978-1841585031 |page=38}} He made many more observations of it, and afterwards Russian Academician Anders Lexell computed the orbit and found it to be probably planetary.{{cite book|last=Kuhn|first=Thomas S.|title=The structure of scientific revolutions|publisher=The University of Chicago Press|location=Chicago|date=1970|isbn=978-0226458045|page=[https://archive.org/details/structureofscie000kuhn/page/115 115]|url=https://archive.org/details/structureofscie000kuhn|url-access=registration}}{{cite journal |last1=Schaffer |first1=Simon |title=Uranus and the Establishment of Herschel's Astronomy |journal=Journal for the History of Astronomy |date=1981 |volume=12 |pages=11–25 |bibcode=1981JHA....12...11S |doi=10.1177/002182868101200102 |s2cid=118813550 }}

Herschel agreed, determining that it must be a planet beyond the orbit of Saturn.[http://www.astroleague.org/al/obsclubs/herschel/fwhershs.html Astronomical League National – Herschel Club – Friedrich Wilhelm Herschel]. Astroleague.org. Retrieved on 5 June 2011. He called the new planet the "Georgian star" (Georgium sidus) after King George III, which also brought him favour; the name did not stick. In France, where reference to the British king was to be avoided if possible, the planet was known as "Herschel" until the name "Uranus" was universally adopted.{{Cite web |title=Remembering William Herschel |url=https://britainsbestguides.org/blogs/remembering-william-herschel/ |access-date=12 June 2024 |website=British Guild of Tourist Guides |language=en-US}} The same year, Herschel was awarded the Copley Medal and elected a Fellow of the Royal Society. In 1782, he was appointed "The King's Astronomer" (not to be confused with the Astronomer Royal).{{cite book |last1=Clerke |first1=Agnes Mary |title=The Herschels and modern astronomy |year=1901 |publisher=New York |location=Cambridge |isbn=978-1108013925 |pages=[https://archive.org/details/herschelsandmod02clergoog/page/n35 30]–35 |url=https://archive.org/details/herschelsandmod02clergoog}}

On 1 August 1782 Herschel and his sister Caroline moved to Datchet (then in Buckinghamshire but now in Berkshire). There, he continued his work as an astronomer and telescope maker.{{harvnb|Holden|1881}} He achieved an international reputation for their manufacture, profitably selling over 60 completed reflectors to British and Continental astronomers.{{harvnb|Mullaney|2007|p=14}}

File:NGC 2683 HST.jpg is an unbarred spiral galaxy discovered by William Herschel on 5 February 1788.]]

From 1782 to 1802, and most intensively from 1783 to 1790, Herschel conducted systematic surveys in search of "deep-sky" or non-stellar objects with two {{convert|20|ft|cm|adj=mid|-focal-length}}, {{convert|12|and|18.7|in|cm|adj=mid|-aperture}} telescopes (in combination with his favoured 6-inch-aperture instrument). Excluding duplicated and "lost" entries, Herschel ultimately discovered over 2,400 objects defined by him as nebulae. (At that time, nebula was the generic term for any visually diffuse astronomical object, including galaxies beyond the Milky Way, until galaxies were confirmed as extragalactic systems by Edwin Hubble in 1924.{{cite magazine|last1=Alfred |first1=Randy |title=Dec. 30, 1924: Hubble Reveals We Are Not Alone |url=https://www.wired.com/2009/12/1230hubble-first-galaxy-outside-milky-way/ |magazine=Wired |access-date=5 June 2018|date=30 December 2009}})

Herschel published his discoveries as three catalogues: Catalogue of One Thousand New Nebulae and Clusters of Stars (1786), Catalogue of a Second Thousand New Nebulae and Clusters of Stars (1789) and the previously cited Catalogue of 500 New Nebulae ... (1802). He arranged his discoveries under eight "classes": (I) bright nebulae, (II) faint nebulae, (III) very faint nebulae, (IV) planetary nebulae, (V) very large nebulae, (VI) very compressed and rich clusters of stars, (VII) compressed clusters of small and large [faint and bright] stars, and (VIII) coarsely scattered clusters of stars. Herschel's discoveries were supplemented by those of Caroline Herschel (11 objects) and his son John Herschel (1754 objects) and published by him as General Catalogue of Nebulae and Clusters in 1864. This catalogue was later edited by John Dreyer, supplemented with discoveries by many other 19th-century astronomers, and published in 1888 as the New General Catalogue (abbreviated NGC) of 7,840 deep-sky objects. The NGC numbering is still the most commonly used identifying label for these celestial landmarks.{{rp|418}}

Herschel's discoveries later compiled in the New General Catalogue include NGC 12, NGC 13, NGC 14, NGC 16, NGC 23, NGC 24, NGC 1357, and NGC 7457.

File:Sir William Herschel and Caroline Herschel. Wellcome V0002731 (cropped).jpg polishing a telescope lens (probably a mirror); 1896 lithograph]]

Following the death of their father, William suggested that Caroline join him in Bath, England. In 1772, Caroline was first introduced to astronomy by her brother.{{Cite web|url=http://m.esa.int/Our_Activities/Space_Science/Herschel/Caroline_and_William_Herschel_Revealing_the_invisible|title=Caroline and William Herschel: Revealing the invisible|last=esa|website=European Space Agency|access-date=24 April 2016}}

Caroline spent many hours polishing the mirrors of high performance telescopes so that the amount of light captured was maximized. She also copied astronomical catalogues and other publications for William. After William accepted the office of King's Astronomer to George III, Caroline became his constant assistant.{{Cite book|title=The Inimitable Caroline|last=Fernie|first=J. Donald|publisher=American Scientist|date=November–December 2007|pages=486–488}}

In October 1783, a new 20-foot telescope came into service for William. During this time, William was attempting to observe and then record all of the observations. He had to run inside and let his eyes readjust to the artificial light before he could record anything, and then he would have to wait until his eyes were adjusted to the dark before he could observe again. Caroline became his recorder by sitting at a desk near an open window. William would shout out his observations and she would write them down along with any information he needed from a reference book.{{Cite book|title=Discoverers of the Universe: William and Caroline Herschel|last=Hoskin |first=Michael|publisher=Princeton University Press|year=2011 |isbn=978-0691148335 }}

Caroline began to make astronomical discoveries in her own right, particularly comets. In 1783, William built her a small Newtonian reflector telescope, with a handle to make a vertical sweep of the sky. Between 1783 and 1787, she made an independent discovery of M110 (NGC 205), which is the second companion of the Andromeda Galaxy. During the years 1786–1797, she discovered or observed eight comets.

She found fourteen new nebulae{{cite web |last1=Redd |first1=Nola Taylor |title=Caroline Herschel Biography |url=https://www.space.com/17439-caroline-herschel.html |website=Space.com|date=4 September 2012}} and, at her brother's suggestion, updated and corrected Flamsteed's work detailing the position of stars.{{cite book |last1=Ogilvie |first1=Marilyn Bailey |title=Searching the stars |date=2008 |publisher=Tempus |location=Stroud |isbn=978-0752442778 |page=146 |url=https://books.google.com/books?id=2LgTDQAAQBAJ&pg=PT46 |access-date=4 June 2018}}{{cite book |last1=Herchsel |first1=Caroline |last2=Flamsteed |first2=John |title=Catalogue of stars taken from Mr Flamsteed's observations contained in the second volume of the Historia Coelestis and not inserted in the British catalogue ... / by Carolina Herschel; with notes & introduction by William Herchsel |date=1798 |publisher=Sold by Peter Elmsly, printer to the Royal society |location=London |url=https://www.royalcollection.org.uk/collection/1191547/catalogue-of-stars-taken-from-mr-flamsteeds-observations-contained-in-the-second |access-date=5 June 2018}} She also rediscovered Comet Encke in 1795.

Caroline Herschel's eight comets were published between 28 August 1782 to 5 February 1787. Five of her comets were published in Philosophical Transactions of the Royal Society. William was even summoned to Windsor Castle to demonstrate Caroline's comet to the royal family. William recorded this phenomenon himself, terming it "My Sister's Comet." She wrote letters to the Astronomer Royal to announce the discovery of her second comet, and wrote to Joseph Banks upon the discovery of her third and fourth comets.{{Cite book|title=Memoir and Correspondence of Caroline Herschel|last=Herschel |first=Caroline|editor-first=Mrs. John|editor-last=Herschel|publisher=John Murray, Albemarle Street |year=1876|location=London|url=http://digital.library.upenn.edu/women/herschel/memoir/memoir.html}}

The Catalogue of stars taken from Mr Flamsteed's observations contained an index of more than 560 stars that had not been previously included. Caroline Herschel was honoured by the Royal Astronomical Society for this work in 1828.{{sfn |Holmes |2008 |p=410}}

Caroline also continued to serve as William Herschel's assistant, often taking notes while he observed at the telescope.{{Cite web|url=http://www.sheisanastronomer.org/index.php/history/carolineherschel|title=Caroline Herschel (1750–1848)|last=Baldwin|first=Emily|website=www.sheisanastronomer.org|access-date=24 April 2016}}

For her work as William's assistant, she was granted an annual salary of £50 by George III. Her appointment made her the first female in England to be honoured with a government position.{{Cite book|title=Women in Science: Antiquity Through the Nineteenth Century|last=Ogilvie|first=Marilyn Bailey|publisher=MIT Press|year=1986|isbn=978-0-262-65038-0|pages=[https://archive.org/details/womeninscience00mari/page/97 97–98]|url=https://archive.org/details/womeninscience00mari/page/97}} It also made her the first woman to be given a salary as an astronomer.{{cite web|last1=Zielinski|first1=Sarah|title=Caroline Herschel: Assistant or Astronomer?|url=https://www.smithsonianmag.com/science-nature/caroline-herschel-assistant-or-astronomer-39807005/|website=smithsonianmag.com|publisher=Smithsonian Institution|access-date=1 April 2018}}

In June 1785, owing to damp conditions, William and Caroline moved to Clay Hall in Old Windsor. On 3 April 1786, the Herschels moved to a new residence on Windsor Road in Slough. Herschel lived the rest of his life in this residence, which came to be known as Observatory House.{{cite web |title=Astronomical observatory |url=https://www.britannica.com/science/astronomical-observatory#ref147669 |website=Encyclopaedia Britannica |access-date=4 June 2018}} It was demolished in 1963.{{cite web |title=Observatory House, about 1900 |url=http://www.sloughhistoryonline.org.uk/ixbin/hixclient.exe?a=query&p=slough&f=generic_objectrecord.htm&_IXFIRST_=1&_IXMAXHITS_=1&%3Dcms_con_core_identifier=sl-sl-673_observatoryhouse-i-00-000.tif&t=sl-sl-williamherschel&s=YsMAJVwNCpg |website=Slough House Online |access-date=5 June 2018}}

William Herschel's marriage in 1788 caused a lot of tension in the brother-sister relationship. Caroline has been referred to as a bitter, jealous woman who worshipped her brother and resented her sister-in-law for invading her domestic life. With the arrival of Mary, Caroline lost her managerial and social responsibilities in the household, and with them much of her status. Caroline destroyed her journals between the years 1788 to 1798, so her feelings during this period are not entirely known. According to her memoir, Caroline then moved to separate lodgings, but continued to work as her brother's assistant. When her brother and his family were away from their home, she would often return to take care of it for them. In later life, Caroline and Lady Herschel exchanged affectionate letters.

Caroline continued her astronomical work after William's death in 1822. She worked to verify and confirm his findings as well as putting together catalogues of nebulae. Towards the end of her life, she arranged two-and-a-half thousand nebulae and star clusters into zones of similar polar distances. She did this so that her nephew, John, could re-examine them systematically. Eventually, this list was enlarged and renamed the New General Catalogue.{{cite journal |last1=Herschel |first1=J. F. W. |title=A General Catalogue of Nebulae and Clusters of Stars for the Year 1860.0, with Precessions for 1880.0 |journal=Proceedings of the Royal Society of London |date=1863–1864 |volume=13 |pages=1–3 |jstor=111986|bibcode=1863RSPS...13....1H }} In 1828, she was awarded the Gold Medal of the Royal Astronomical Society for her work.{{cite web |title=Awards, Medals and Prizes Winners of the Gold Medal of the Royal Astronomical Society |url=https://www.ras.org.uk/awards-and-grants/awards/268 |website=Royal Astronomical Society |access-date=5 June 2018 |archive-url=https://web.archive.org/web/20160630050255/http://www.ras.org.uk/awards-and-grants/awards/268/ |archive-date=30 June 2016 |url-status=dead }}

The most common type of telescope at that time was the refracting telescope, which involved the refraction of light through a tube using a convex glass lens.

This design was subject to chromatic aberration, a distortion of an image due to the failure of light of different component wavelengths to converge. Optician John Dollond (1706–1761) tried to correct for this distortion by combining two separate lenses, but it was still difficult to achieve good resolution for far distant light sources.

Reflector telescopes, invented by Isaac Newton in 1668, used a single concave mirror rather than a convex lens. This avoids chromatic aberration. The concave mirror gathered more light than a lens, reflecting it onto a flat mirror at the end of the telescope for viewing. A smaller mirror could provide greater magnification and a larger field of view than a convex lens. Newton's first mirror was 1.3 inches in diameter; such mirrors were rarely more than 3 inches in diameter.

Because of the poor reflectivity of mirrors made of speculum metal, Herschel eliminated the small diagonal mirror of a standard newtonian reflector from his design and tilted his primary mirror so he could view the formed image directly. This "front view" design has come to be called the Herschelian telescope.{{cite journal |last1=Maurer |first1=A. |last2=Forbes |first2=E. G. |title=William Herschel's Astronomical Telescopes |journal=Journal of the British Astronomical Association |date=1971 |volume=81 |pages=284–291 |bibcode=1971JBAA...81..284M }}{{cite book|last1=Bratton|first1=Mark|title=The complete guide to the Herschel objects : Sir William Herschel's star clusters, nebulae, and galaxies|date=2011|publisher=Cambridge University Press|location=Cambridge |isbn=978-0521768924|page=7|url=https://books.google.com/books?id=JLuv9bAUbBwC&pg=PA6|access-date=17 May 2018}}{{rp|7}}

The creation of larger, symmetrical mirrors was extremely difficult. Any flaw would result in a blurred image. Because no one else was making mirrors of the size and magnification desired by Herschel, he determined to make his own. This was no small undertaking. He was assisted by his sister Caroline and other family members. Caroline Herschel described the pouring of a 30-foot-focal-length mirror:

{{blockquote|A day was set apart for casting, and the metal was in the furnace, but unfortunately it began to leak at the moment when ready for pouring, and both my brothers and the caster with his men were obliged to run out at opposite doors, for the stone flooring (which ought to have been taken up) flew about in all directions, as high as the ceiling. My poor brother fell, exhausted with heat and exertion, on a heap of brickbats. Before the second casting was attempted, everything which could ensure success had been attended to, and a very perfect metal was found in the mould, which had cracked in the cooling.|Caroline Herschel}}

Herschel is reported to have cast, ground, and polished more than four hundred mirrors for telescopes, varying in size from 6 to 48 inches in diameter.{{cite journal|last1=Hastings|first1=C. S.|title=History of the telescope|journal=The Sidereal Messenger: A Monthly Review of Astronomy|date=1891|volume=10|page=342 |url=https://books.google.com/books?id=dMBLAAAAYAAJ&pg=PA342|access-date=17 May 2018}} Herschel and his assistants built and sold at least sixty complete telescopes of various sizes.

Commissions for the making and selling of mirrors and telescopes provided Herschel with an additional source of income. The King of Spain reportedly paid £3,150 for a telescope.

An essential part of constructing and maintaining telescopes was the grinding and polishing of their mirrors. This had to be done repeatedly, whenever the mirrors deformed or tarnished during use.

The only way to test the accuracy of a mirror was to use it.

{{see also|40-foot telescope}}

File:Lossy-page1-3705px-Herschel's Grand Forty feet Reflecting Telescopes RMG F8607 (cropped).jpg]]

The largest and most famous of Herschel's telescopes was a reflecting telescope with a 49{{frac|1|2}}-inch-diameter (1.26 m) primary mirror and a {{convert|40|ft|adj=on}} focal length. The 40-foot telescope was, at that time, the largest scientific instrument that had been built. It was hailed as a triumph of "human perseverance and zeal for the sublimest science".{{rp|215}}

In 1785 Herschel approached King George for money to cover the cost of building the 40-foot telescope. He received £4,000. Without royal patronage, the telescope could not have been created. As it was, it took five years, and went over budget.

The Herschel home in Slough became a scramble of "labourers and workmen, smiths and carpenters". A 40-foot telescope tube had to be cast of iron. The tube was large enough to walk through. Mirror blanks were poured from Speculum metal, a mix of copper and tin. They were almost {{convert|4|ft|m|spell=in}} in diameter and weighed {{convert|1,000|lb|kg}}. When the first disk deformed due to its weight, a second thicker one was made with a higher content of copper. The mirrors had to be hand-polished, a painstaking process. A mirror was repeatedly put into the telescope and removed again to ensure that it was properly formed. When a mirror deformed or tarnished, it had to be removed, repolished and replaced in the apparatus. A huge rotating platform was built to support the telescope, enabling it to be repositioned by assistants as a sweep progressed. A platform near the top of the tube enabled the viewer to look down into the tube and view the resulting image.{{cite web|title=40-foot Herschelian (reflector) telescope tube remains – National Maritime Museum|url=http://collections.rmg.co.uk/collections/objects/11109.html |website=Royal Museums Greenwich |access-date=5 June 2018}}

File:PIA06256 Mimas full view.jpg orbiter's view of Mimas, a moon of Saturn discovered by Herschel in 1789]]

In 1789, shortly after this instrument was operational, Herschel discovered a new moon of Saturn: Mimas, only {{convert|250|mi|km}} in diameter.{{sfn|Holmes|2008 |pp=190}} Discovery of a second moon (Enceladus) followed, within the first month of observation.

The {{convert|40|ft|m|abbr=off|adj=on}} telescope proved very cumbersome, and in spite of its size, not very effective at showing clearer images. Herschel's technological innovations had taken him to the limits of what was possible with the technology of his day. The 40-foot would not be improved upon until the Victorians developed techniques for the precision engineering of large, high-quality mirrors.{{cite journal|last1=Chapman|first1=A. |title=William Herschel and the Measurement of Space |journal=Quarterly Journal of the Royal Astronomical Society |date=1989 |volume=30 |issue=4 |pages=399 |bibcode=1989QJRAS..30..399C}}

William Herschel was disappointed with it.{{cite journal|last1= Roberts |first1=Jacob |title=A Giant of Astronomy |journal=Distillations |date=2017|volume=3|issue=3 |pages=6–11 |url=https://www.sciencehistory.org/distillations/magazine/a-giant-of-astronomy}}{{cite book |last1=Ceragioli |first1=R. |editor-last=Cunningham |editor-first=C. |title=The Scientific Legacy of William Herschel |chapter=William Herschel and the "Front-View" Telescopes |date=2018 |publisher=Springer |location=Cham |pages=97–238 |doi=10.1007/978-3-319-32826-3_4 |series=Historical & Cultural Astronomy |isbn=978-3-319-32825-6 }}

Most of Herschel's observations were done with a smaller {{convert|18.5|in|cm|adj=on}}, {{convert|20|ft|m|adj=mid|-focal-length}} reflector. Nonetheless, the 40-foot caught the public imagination. It inspired scientists and writers including Erasmus Darwin and William Blake, and impressed foreign tourists and French dignitaries. King George was pleased.

Herschel discovered that unfilled telescope apertures can be used to obtain high angular resolution, something which became the essential basis for interferometric imaging in astronomy (in particular aperture masking interferometry and hypertelescopes).{{cite journal |last1=Baldwin |first1=J. E. |last2=Haniff |first2=C. A. |title=The application of interferometry to optical astronomical imaging |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |date=15 May 2002 |volume=360 |issue=1794 |pages=969–986 |doi=10.1098/rsta.2001.0977 |pmid=12804289 |bibcode=2002RSPTA.360..969B |s2cid=21317560 }}

In 2012, the BBC television programme Stargazing Live built a replica of the 20-foot telescope using Herschel's original plans but modern materials. It is to be considered a close modern approximation rather than an exact replica. A modern glass mirror was used, the frame uses metal scaffolding and the tube is a sewer pipe. The telescope was shown on the programme in January 2013 and stands on the Art, Design, and Technology campus of the University of Derby where it will be used for educational purposes.{{cite web |title=BBC builds William Herschel's telescope for Stargazing Live |url=http://www.bbc.co.uk/ariel/20970167 |website=BBC/Ariel |access-date=10 January 2013 |archive-url=https://web.archive.org/web/20190414083220/http://www.bbc.co.uk/ariel/20970167 |archive-date=14 April 2019 |url-status=dead }}

Herschel was sure that he had found ample evidence of life on the Moon and compared it to the English countryside. He did not refrain himself from theorising that the other planets were populated, with a special interest in Mars, which was in line with most of his contemporary scientists. During Herschel's time, scientists tended to believe in a plurality of civilised worlds; in contrast, most religious thinkers referred to unique properties of the Earth.{{cite book|last1=Basalla|first1=George|title=Civilized life in the universe : scientists on intelligent extraterrestrials|date=2006|publisher=Oxford University Press|location=New York|isbn=978-0195171815|page=[https://archive.org/details/civilizedlifeinu0000basa/page/52 52]|url=https://archive.org/details/civilizedlifeinu0000basa/page/52}}

Herschel went so far as to speculate that the interior of the Sun was populated.

Herschel examined the correlation of solar variation and solar cycle and climate.{{cite journal |last=Herschel |first=W. |date=1801 |title=Observations tending to investigate the nature of the Sun, in order to find the causes or symptoms of its variable emission of light and heat; With remarks on the use that may possibly be drawn from solar observations |journal=Philosophical Transactions of the Royal Society of London |volume=91 |pages=265–318 |jstor=107097 |bibcode=1801RSPT...91..265H |doi=10.1098/rstl.1801.0015|doi-access=free }} Over a period of 40 years (1779–1818), Herschel regularly observed sunspots and their variations in number, form and size. Most of his observations took place in a period of low solar activity, the Dalton Minimum, when sunspots were relatively few in number. This was one of the reasons why Herschel was not able to identify the standard 11-year period in solar activity.{{cite journal|last1=Ball|first1=Philip|title=Sun set food prices in the Middle Ages|journal=Nature|date=22 December 2003|doi=10.1038/news031215-12|url=https://www.nature.com/news/2003/031222/full/news031215-12.html|access-date=17 May 2018|url-access=subscription}}{{cite journal|last1=Pustil'nik|first1=Lev A.|last2=Din|first2=Gregory Yom|title=Influence of solar activity on the state of the wheat market in medieval England|journal=Solar Physics|date=September 2004|volume=223|issue=1–2|pages=335–356|doi=10.1007/s11207-004-5356-5|arxiv=astro-ph/0312244|bibcode=2004SoPh..223..335P|s2cid=55852885}}

Herschel compared his observations with the series of wheat prices published by Adam Smith in The Wealth of Nations.{{cite book|last1=Nye|first1=Mary Jo|title=The Cambridge History of Science: Volume 5, The Modern Physical and Mathematical Sciences |volume=5| date=2003|publisher=Cambridge University Press|location=Cambridge|isbn= 978-0521571999 |page=508}}

In 1801, Herschel reported his findings to the Royal Society and indicated five prolonged periods of few sunspots correlated with the price of wheat. Herschel's study was ridiculed by some of his contemporaries but did initiate further attempts to find a correlation. Later in the 19th century, William Stanley Jevons proposed the 11-year cycle with Herschel's basic idea of a correlation between the low number of sunspots and lower yields explaining recurring booms and slumps in the economy.

Herschel's speculation on a connection between sunspots and regional climate, using the market price of wheat as a proxy, continues to be cited.

According to one study, the influence of solar activity can actually be seen on the historical wheat market in England over ten solar cycles between 1600 and 1700. The evaluation is controversial{{cite journal|title=Solar Influence on Global and Regional Climates | doi=10.1007/s10712-012-9181-3 | volume=33|issue=3–4 |journal=Surveys in Geophysics|pages=503–534 | last1 = Lockwood | first1 = Mike|bibcode = 2012SGeo...33..503L |year=2012 |doi-access=free }} and the significance of the correlation is doubted by some scientists.{{cite journal |last=Love |first=J. J. |date=2013 |title=On the insignificance of Herschel's sunspot correlation |journal=Geophysical Research Letters |volume=40 |issue=16 |pages=4171–4176 |doi=10.1002/grl.50846 |url=https://geomag.usgs.gov/downloads/publications/grl50846.pdf |bibcode=2013GeoRL..40.4171L |citeseerx=10.1.1.377.257 |s2cid=1654166 }}

In his later career, Herschel discovered two moons of Saturn, Mimas{{cite web |title=Mimas |url=https://solarsystem.nasa.gov/moons/saturn-moons/mimas/in-depth/ |website=NASA Science Solar System Exploration |date=5 December 2017 |access-date=5 June 2018}} and Enceladus;{{cite web |title=Enceladus |url=https://solarsystem.nasa.gov/moons/saturn-moons/enceladus/in-depth/ |website=NASA Science Solar System Exploration |date=20 November 2017 |access-date=5 June 2018}} as well as two moons of Uranus, Titania and Oberon.{{cite news |last1=Franz |first1=Julia |title=Why the moons of Uranus are named after characters in Shakespeare |url=https://www.pri.org/stories/2017-01-01/why-moons-uranus-are-named-after-characters-shakespeare|work=Studio 360 |date=1 January 2017}} He did not give these moons their names; they were named by his son John in 1847 and 1852, respectively, after his death. Herschel measured the axial tilt of Mars{{cite web |title=All About Mars |url=https://mars.nasa.gov/allaboutmars/mystique/history/1700/ |website=NASA Mars Exploration |access-date=5 June 2018}} and discovered that the Martian ice caps, first observed by Giovanni Domenico Cassini (1666) and Christiaan Huygens (1672), changed size with that planet's seasons.{{cite web |title=Mars in the Classroom |url=http://zuserver2.star.ucl.ac.uk/~rpif/mitc/mitcearly.html |website=Copus |access-date=5 June 2018 |archive-date=29 December 2017 |archive-url=https://web.archive.org/web/20171229034956/http://zuserver2.star.ucl.ac.uk/~rpif/mitc/mitcearly.html |url-status=dead }} It has been suggested that Herschel discovered rings around Uranus.{{cite news |url=http://news.bbc.co.uk/2/hi/sci/tech/6569849.stm |work=BBC News |first=Paul |last=Rincon |title=Uranus rings 'were seen in 1700s' |date=18 April 2007}}

Herschel introduced but did not create the word "asteroid",In an oral presentation ({{cite web|url=http://had.aas.org/meetings/2013bAbstracts.html#HADII|title=HAD Meeting with DPS, Denver, October 2013 – Abstracts of Papers|access-date=14 October 2013|url-status=dead|archive-url=https://web.archive.org/web/20140901143955/http://had.aas.org/meetings/2013bAbstracts.html#HADII|archive-date=1 September 2014}}), Clifford Cunningham presented his finding that the word has been coined by Charles Burney, Jr., the son of a friend of Herschel, see {{cite news|title=Local expert reveals who really coined the word 'asteroid'|url=http://www.sun-sentinel.com/news/broward/fl-asteroid-word-origin-20131008,0,501498,full.story|date=8 October 2013|access-date=10 October 2013|newspaper=South Florida Sun-Sentinel|archive-date=30 November 2014|archive-url=https://archive.today/20141130155012/http://www.sun-sentinel.com/news/broward/fl-asteroid-word-origin-20131008,0,501498,full.story|url-status=dead}}. See also {{cite web|url=http://www.space.com/10593-post-william-herschel-coin-term-asteroid.html|title=Who Really Invented the Word 'Asteroid' for Space Rocks?|last=Wall|first=Mike|publisher=SPACE.com|date=10 January 2011|access-date=10 October 2013}} meaning star-like (from the Greek asteroeides, aster "star" + -eidos "form, shape"), in 1802 (shortly after Olbers discovered the second minor planet, 2 Pallas, in late March), to describe the star-like appearance of the small moons of the giant planets and of the minor planets; the planets all show discs, by comparison. By the 1850s 'asteroid' became a standard term for describing certain minor planets.{{cite news |last1=Williams |first1=Matt |title=What is the asteroid belt? |url=https://phys.org/news/2015-08-asteroid-belt.html|work=Universe Today |date=24 August 2015}}

From studying the proper motion of stars, the nature and extent of the solar motion was first demonstrated by Herschel in 1783, along with first determining the direction for the solar apex to Lambda Herculis, only 10° away from today's accepted position.{{cite book | first=John | last=Lankford | date=1997 | title=History of astronomy: an encyclopedia | page=[https://archive.org/details/historyofastrono00john/page/258 258] | volume=1 | series=Garland encyclopedias in the history of science | publisher=Taylor & Francis | isbn=978-0-8153-0322-0 | url=https://archive.org/details/historyofastrono00john/page/258 }}{{cite journal |jstor=106492 |last1=Herschel |first1=William |date=1783 |title=On the Proper Motion of the Sun and Solar System; With an Account of Several Changes That Have Happened among the Fixed Stars since the Time of Mr. Flamstead [sic] |journal=Philosophical Transactions of the Royal Society of London |volume=73 |pages=247–283 |doi=10.1098/rstl.1783.0017 |s2cid=186213288 }}{{citation | title=Herschel's Determination of the Solar Apex | last1=Hoskin | first1=M. | journal=Journal for the History of Astronomy | volume=11 | issue=3 | pages=153–163 | year=1980 | bibcode=1980JHA....11..153H | postscript=. | doi=10.1177/002182868001100301| s2cid=115478560 }}

File:Herschel-galaxy.jpg

Herschel also studied the structure of the Milky Way and was the first to propose a model of the galaxy based on observation and measurement.{{cite journal |last1=Herschel |first1=William |title=XII. On the construction of the heavens |journal=Philosophical Transactions of the Royal Society of London |date=1 January 1785 |volume=75 |pages=213–266 |doi=10.1098/rstl.1785.0012 |s2cid=186213203 |doi-access=free }} He concluded that it was in the shape of a disk, but incorrectly assumed that the Sun was in the centre of the disk.{{cite journal |last1=Berendzen |first1=Richard |title=Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric |journal=Vistas in Astronomy |date=1975 |volume=17 |issue=1 |pages=65–83 |doi=10.1016/0083-6656(75)90049-5 |bibcode=1975VA.....17...65B }}{{cite web |title=The Shape of the Milky Way from Starcounts |url=https://www.e-education.psu.edu/astro801/content/l8_p3.html |website=Astro 801 |access-date=5 June 2018}}{{Citation |url=https://www.pbs.org/seeinginthedark/meet-the-stargazers/in-history.html |title=Stargazers in History |publisher=PBS }} This heliocentric view was eventually replaced by galactocentrism due to the work of Harlow Shapley, Heber Doust Curtis and Edwin Hubble in the 20th century. All three men used significantly more far-reaching and accurate telescopes than Herschel's.{{Citation |title=The Galactocentric Revolution, A Reminiscent Narrative |date=October 1965 |last=van de Kamp |first=Peter |journal=Publications of the Astronomical Society of the Pacific |volume=77 |pages=324–328 |issue=458 |bibcode=1965PASP...77..325V |doi = 10.1086/128228 |doi-access=free }}{{cite journal |last1=Bergh |first1=Sidney van den |title=Hubble and Shapley—Two Early Giants of Observational Cosmology |journal=Journal of the Royal Astronomical Society of Canada |date=2011 |volume=105 |issue=6 |pages=245 |arxiv=1110.2445 |bibcode=2011JRASC.105..245V }}

In early 1800, Herschel was testing different filters to pass sunlight through, and noticed that filters of different colors seemed to generate varying amounts of heat. He decided to pass the light through a prism to measure the different colors of light using a thermometer, and in the process, took a measurement just beyond the red end of the visible spectrum. He detected a temperature one degree higher than that of red light. Further experimentation led to Herschel's conclusion that there must be an invisible form of light beyond the visible spectrum.{{cite book |first=Michael |last=Rowan-Robinson |date=2013 |title=Night Vision: Exploring the Infrared Universe |page=23 |publisher=Cambridge University Press |isbn=9781107024762 |oclc=780161457}}{{cite book|last1=Aughton|first1=Peter|title=The story of astronomy|date=2011|publisher=Quercus|location=New York|isbn=978-1623653033|url=https://books.google.com/books?id=vpeJAwAAQBAJ&pg=PT96|access-date=17 May 2018}} He published these results in April 1800.{{cite journal|last=Herschel|first=William|year=1800|title=Experiments on the refrangibility of the invisible rays of the Sun|url=https://babel.hathitrust.org/cgi/pt?id=pst.000054592520;view=1up;seq=358|journal=Philosophical Transactions of the Royal Society of London|volume=90|pages=284–292|doi=10.1098/rstl.1800.0015|jstor=107057|doi-access=free|url-access=subscription}}

Herschel used a microscope to establish that coral was not a plant – as many at the time believed – because it lacked the cell walls characteristic of plants. It is in fact an animal, a marine invertebrate.{{cite book|last1=Azzouni|first1=Jody|title=Ontology Without Borders|date=20 July 2017|publisher=Oxford University Press|isbn=9780190622558|url=https://books.google.com/books?id=0W4sDwAAQBAJ&pg=PT69}}

File:Arms of William Herschel.svg:George Thomas Clark (1809–1898), article on heraldry in the Encyclopaedia Britannica (9th & 10th editions)[https://www.1902encyclopedia.com/H/HER/heraldry-13.html] Argent, on a mount vert a representation of the 40 ft. reflecting telescope with its apparatus proper on a chief azure the astronomical symbol of Uranus irradiated or. Crest: A demi terrestrial sphere proper thereon an eagle, wings elevated or]]

On 8 May 1788, William Herschel married the widow Mary Pitt (née Baldwin) at St Laurence's Church, Upton in Slough.{{sfn |Holmes |2008 |pp=186}} They had one child, John, born at Observatory House on 7 March 1792. William's personal background and rise as man of science had a profound impact on the upbringing of his son and grandchildren. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1788.{{cite web|title=Book of Members, 1780–2010: Chapter H|url=http://www.amacad.org/publications/BookofMembers/ChapterH.pdf|publisher=American Academy of Arts and Sciences|access-date=28 July 2014}} In 1816, William was made a Knight of the Royal Guelphic Order by the Prince Regent and was accorded the honorary title 'Sir' although this was not the equivalent of an official British knighthood.{{cite journal |last1=Hanham |first1=A. |first2=M. |last2=Hoskin |journal=Journal for the History of Astronomy |volume=44 |title=The Herschel Knighthoods: Facts and Fiction |name-list-style=amp |bibcode=2013JHA....44..149H |issue=120 |pages=149–164 |date=2013|doi=10.1177/002182861304400202 |s2cid=118171124 }} He helped to found the Astronomical Society of London in 1820,{{cite journal |last1=Shortland |first1=E. |title=The Astronomical Society of London |journal=Journal of the British Astronomical Association |date=1820 |volume=81 |pages=44–47 |url=http://adsbit.harvard.edu/full/seri/JBAA./0081//0000044.000.html |access-date=6 June 2018}} which in 1831 received a royal charter and became the Royal Astronomical Society.{{cite web |title=A brief history of the RAS |url=https://www.ras.org.uk/about-the-ras/a-brief-history |website=Royal Astronomical Society |access-date=6 June 2018}} In 1813, he was elected a foreign member of the Royal Swedish Academy of Sciences.

On 25 August 1822, Herschel died at Observatory House, Windsor Road, Slough, Buckinghamshire, after a long illness. Caroline was deeply distressed by his death, and soon after his burial she returned to Hanover, a decision she later regretted. She had lived in England for fifty years. Her interests were much more in line with her nephew John Herschel, also an astronomer, than with her surviving family in Hanover. She continued to work on the organization and cataloguing of nebulae, creating what would later become the basis of the New General Catalogue. She died on 9 January 1848.{{Cite journal|last1=Olson|first1=Roberta J. M.|author1-link=Roberta Olson |last2=Pasachoff |first2=Jay M.|date=2012|title=The Comets of Caroline Herschel (1750–1848), Sleuth of the Skies at Slough|journal=Culture and Cosmos|volume=16 |pages=53–80 |doi=10.46472/CC.01216.0213 |arxiv=1212.0809 |bibcode=2012arXiv1212.0809O |s2cid=117934098 }}{{Cite web|url=http://www.space.com/17439-caroline-herschel.html|title=Caroline Herschel Biography|website=Space.com|date=4 September 2012|access-date=23 April 2016}}

File:William Herschel Museum - IOP plaque.jpg in Bath]]

William Herschel lived most of his life in the town of Slough, then in Buckinghamshire (now in Berkshire). He died in the town and was buried under the tower of the nearby St Laurence's Church, Upton-cum-Chalvey.{{cite web |title=Our History |url=http://www.saint-laurence.com/history.html |website=Saint Laurence Church, Upton-cum-Chalvey, Slough |access-date=6 June 2018}} Herschel's epitaph is:

{{blockquote|Coelorum perrupit claustra
(He broke through the barriers of the heavens){{cite book|last1=Pendergrast|first1=Mark|title=Mirror mirror : a history of the human love affair with reflection |date=2004|publisher=Basic Books|location=New York|isbn=978-0465054718|page=159|url=https://books.google.com/books?id=T4-GErgSbU0C&pg=PA159|access-date=17 May 2018}}}}

Herschel is especially honoured in Slough and there are several memorials to him and his discoveries. In 2011 a new bus station, the design of which was inspired by the infrared experiment of William Herschel, was built in the centre of Slough.

John Keats alludes to Herschel's discovery of Uranus in his 1816 sonnet "On First Looking into Chapman's Homer": "Then felt I like some watcher of the skies/ When a new planet swims into his ken." Richard Holmes says that Keats "picks out the finding of Uranus, thirty-five years before, as one of the defining moments of the age."{{sfn|Holmes|2008|p=206}}

His house at 19 New King Street in Bath, Somerset, where he made many telescopes and first observed Uranus, is now home to the Herschel Museum of Astronomy.{{cite web |title=Visiting |url=http://herschelmuseum.org.uk/visiting/ |website=Herschel Museum of Astronomy |access-date=6 June 2018}} There is a commemorative plaque installed by the Institute of Physics.

There is a memorial near the choir screen in Westminster Abbey.'The Abbey Scientists' Hall, A.R. p53: London; Roger & Robert Nicholson; 1966

Herschel's complete musical works are as follows:{{cite web |url=http://asterope.bajaobs.hu/cski/research/mktars/hegecikk/WilliamHerschel.htm |archive-url=https://archive.today/20130625154724/http://asterope.bajaobs.hu/cski/research/mktars/hegecikk/WilliamHerschel.htm |url-status=dead |archive-date=25 June 2013 |title=William Herschel (1738–1822): Organ works |publisher=asterope.bajaobs.hu |access-date=1 May 2013 }}

• 18 symphonies for small orchestra (1760–1762)
• 6 symphonies for large orchestra (1762–1764)
• 12 concertos for oboe, violin and viola (1759–1764)
• 2 concertos for organ
• 6 sonatas for violin, cello and harpsichord (published 1769)
• 12 solos for violin and basso continuo (1763)
• 24 capriccios and 1 sonata for solo violin
• 1 andante for two basset horns, two oboes, two horns and two bassoons.

Various vocal works including a "Te Deum", psalms, motets and sacred chants along with some catches.

Keyboard works for organ and harpsichord:

• 6 fugues for organ
• 24 sonatas for organ (10 now lost)
• 33 voluntaries and pieces for organ (incomplete)
• 24 pieces for organ (incomplete)
• 12 voluntaries (11 now lost)
• 12 sonatas for harpsichord (9 extant)
• 25 variations on an ascending scale
• 2 minuets for harpsichord

File:William Herschel.jpg, c. 1805]]

• The astrological symbol for planet Uranus (22px) features the capital initial letter of Herschel's surname.
• Mu Cephei is also known as Herschel's Garnet Star
• Herschel, a crater on the Moon
• Herschel, a large impact basin on Mars
• The enormous crater Herschel on Saturn's moon Mimas
• The Herschel gap in Saturn's rings.
• 2000 Herschel, an asteroid
• The William Herschel Telescope on La Palma
• The Herschel Space Observatory, successfully launched by the European Space Agency on 14 May 2009. It was the largest space telescope of its kind, until the launch of the James Webb Space Telescope.
• Herschel Grammar School, Slough
• Rue Herschel, a street in the 6th arrondissement of Paris.
• The Herschel Building at Bath College, Bath
• The Herschel building at Newcastle University, Newcastle, United Kingdom
• Herschel Museum of Astronomy, at 19 New King Street in Bath.
• Herschelschule, Hanover, Germany, a grammar school
• The Herschel Observatory, at the Universitas School in Santos, Brazil.
• The lunar crater C. Herschel, the asteroid 281 Lucretia, and the comet 35P/Herschel-Rigollet are named after his sister Caroline Herschel.
• The public house "Herschel Arms" at 22 Park Street, Slough is named after him and is quite close to the site of Observatory House.
• Herschel Astronomical Society, the operator of the Herschel Memorial Observatory based in Eton, Berkshire.
• Herschel Park, Slough.
• The shape of Slough Bus Station, built in 2011, was inspired by Herschel's infrared experiment.{{cite news |last=Serck |first=Linda |url=https://www.bbc.co.uk/news/uk-england-berkshire-13527012 |title=Slough bus station: Silver dolphin or beached whale? |work=bbc.co.uk |date=28 May 2011 |access-date=13 August 2012}}
• Herschel Street, a street in Brisbane, Australia.

• Catalogue of Nebulae and Clusters of Stars
• German inventors and discoverers
• List of astronomical instrument makers
• List of largest optical telescopes historically
• NGC 4800
• NGC 4694

• Sophia Elizabeth Herschel (1733–1803) – in 1755 married violinist Johann Heinrich Griesbach (1730–1773), she lived in Hannover all her life, and had seven children.
• {{ill|Heinrich Anton Jacob Herschel|de|Jacob Herschel}} (1734–1792) – musician, unmarried
• Johann Heinrich Herschel (1736–1743)
• Anna Christina Herschel (1741–1748) – died of whooping cough.
• Johann Alexander Herschel (1745–1821) – he was married to Margarethe Smith, no children.
• Maria Dorothea Herschel (1748–1749)
• Caroline Lucretia Herschel (1750–1848)
• Franz Johann Herschel (1752–1754) – died from smallpox.
• Johann Dietrich Herschel (1755–1827) – musician, he married Catharina Maria Reiff (1760–1846) and had four children.

{{reflist|30em}}

• {{cite wikisource |last=Holden |first=Edward S. |date=1881 |author-link=Edward S. Holden |title=Sir William Herschel, his life and works |publisher=Charles Scribner's Sons |location=New York}}
• {{cite book |last=Holmes |first=Richard |date=2008 |title=The age of wonder |publisher=Vintage Books |location=New York |isbn=978-1-4000-3187-0}}
• {{cite book |last=Mullaney |first=James |date=2007 |title=The Herschel objects and how to observe them |publisher=Springer |url=https://books.google.com/books?id=HFg2sOjrFtsC&pg=PA10 |access-date=5 June 2011 |isbn=978-0-387-68124-5}}

• {{Cite EB1911|wstitle= Herschel, Sir Frederick William | volume= 13 |last1= Clerke |first1= Agnes Mary |author1-link= Agnes Mary Clerke |last2= Pritchard |first2= Charles |author2-link= Charles Pritchard | pages = 391–393 |short=1|ref=none}}
• "William Herschel" by Michael Hoskin. New Dictionary of Scientific Biography Scribners, 2008. v. 3, pp. 289–291.
• [http://adsabs.harvard.edu//full/seri/JRASC/0074//0000134.000.html Biography: JRASC 74 (1980) 134]

{{library resources box|by=yes|onlinebooksby=yes |viaf=19885773|lcheading=Herschel, William, 1738–1822}}

• {{Commons category-inline}}

{{Wikiquote}}

• {{wikisource author-inline}}
• [http://rstl.royalsocietypublishing.org/search?fulltext=william+herschel&submit=yes&andorexactfulltext=and&x=35&y=7 Articles and letters published in the Philosophical Transactions and available online] (70 items, June 2016)
• [http://messier.seds.org/xtra/similar/herschel.html William Herschel's Deep Sky Catalog]
• [http://www.handprint.com/ASTRO/herschel.html The William Herschel Double Star Catalogs Restored]
• Full text of {{Ws | Herschel by Hector Macpherson}}
• Full text of [https://gutenberg.org/etext/12340 The Story of the Herschels] (1886) from Project Gutenberg
• [http://www.npg.org.uk/live/search/person.asp?search=ss&sText=herschel&LinkID=mp02166 Portraits of William Herschel] {{Webarchive|url=https://web.archive.org/web/20070930192346/http://www.npg.org.uk/live/search/person.asp?search=ss&sText=herschel&LinkID=mp02166 |date=30 September 2007 }} at the National Portrait Gallery (United Kingdom)
• [http://www.bath-preservation-trust.org.uk/ Herschel Museum of Astronomy] located in his Bath home
• [http://herschelsociety.org.uk/ William Herschel Society]
• [https://books.google.com/books?id=Ml6DwyLbxdIC The Oboe Concertos of Sir William Herschel, Wilbert Davis Jerome ed.] {{ISBN|0-87169-225-2}}
• [http://contentdm.lindahall.org/u?/classics,4720 A notebook of Herschel's, dated from 1759] {{Webarchive|url=https://web.archive.org/web/20190109111114/http://contentdm.lindahall.org/u?%2Fclassics%2C4720 |date=9 January 2019 }} is available in the digital collections of the Linda Hall Library.
• [http://digitalcollections.ucsc.edu/cdm/search/collection/p265101coll10/searchterm/%20Herschel/order/title Portraits of William Herschel (and other members of the family) from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections] {{Webarchive|url=https://web.archive.org/web/20160304191407/http://digitalcollections.ucsc.edu/cdm/search/collection/p265101coll10/searchterm/%20Herschel/order/title |date=4 March 2016 }}
• Michael Lemonick: [https://web.archive.org/web/20120721161044/http://www-ppd.fnal.gov/EPPOffice-w/colloq/colloq_08_09.html William Herschel, the First Observational Cosmologist], 12 November 2008, Fermilab Colloquium
• {{IMSLP|id=Herschel, William}}
• Musical pieces by William Herschel @YouTube:
• {{YouTube|hXZ6olVNh4w|Chamber Symphony in F minor No. 4- Allegro moderato (I)}}
• {{YouTube|efk3fm1B0zc|Hubble Images to Herschel Music}} (Chamber Symphony in F, 2nd movement)
• {{YouTube|MRe7_9lxPns|Richmond Sinfonia for Strings, Bassoon & Harpsichord n. 2 in D major}}
• {{YouTube|7BehLlyqYk8|Sinfonía para Cuerdas No. 8 en Do menor}}
• {{YouTube|O9ZA0gA4Qps|Sinfonia n. 12, primo movimento, Allegro}}
• {{YouTube|Ry8_v-nYdqg|Symphony No. 8, I: Allegro Assai}}

{{Copley Medallists 1751-1800}}

{{Uranus}}

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