Christopher David Impey (born 25 January 1956) is a British astronomer, educator, and author.
 He has been a faculty member at the University of Arizona since 1986.
 Impey has done research on observational cosmology, in particular low surface brightness galaxies, the intergalactic medium, and surveys of active galaxies and quasars.
 As an educator, he has pioneered the use of instructional technology for teaching science to undergraduate non-science majors.
 He has written many technical articles and a series of popular science books: "The Living Cosmos", "", "How It Began", "Dreams of Other Worlds", and "Humble Before the Void".
 He served as Vice-President of the American Astronomical Society, he is a Fellow of the American Association for the Advancement of Science, and a Howard Hughes Medical Institute Professor.
John Henry Reynolds (1874–1949) was a British astronomer who served as the president of the Royal Astronomical Society between 1935 and 1937 and is known for his work on the classification of stellar bodies.
 An amateur, he was the son of Alfred John Reynolds, the Lord Mayor of Birmingham, who owned a company which cut nails.
 In 1899, at age 25, he was elected a Fellow of the Royal Astronomical Society and in 1907, he financed the construction of a 30-inch reflecting telescope in Helwan, Egypt, the first large telescope to study objects in the such southerly skies.
 He also hand-constructed a 28-inch telescope in Harborne.
 Images from the Reynolds telescope was later used by Gérard de Vaucouleurs in his system of classifying galaxies; Reynolds also published his own classification for spiral galaxies in 1920.
 Edwin Hubble frequently corresponded with Reynolds, and some of his findings into the classification of stellar bodies seems at least inspired by his work.
 The Hubble–Reynolds law, a formula for measuring the surface brightness of elliptical galaxies, is named after them.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer.
 He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.
Edwin Hubble House is a National Historic Landmark house located at 1340 Woodstock Road, in San Marino, California.
 It was the home of astronomer Edwin Hubble.
 He lived there from 1925 until he died in 1953, and the house remained in the Hubble family until approximately 1973.
The President of the Royal Astronomical Society (prior to 1831 known as President of the Astronomical Society of London) chairs the Council of the Royal Astronomical Society (RAS) and its formal meetings.
 They also liaise with government organisations (including the Department for Business, Innovation and Skills and the UK Research Councils), similar societies in other countries, and the International Astronomical Union on behalf of the UK astronomy and geophysics communities.
 Future presidents serve one year as President Elect before succeeding the previous president.
Alice Grace Cook (1877 - 27 May 1958), known as Grace Cook or A. Grace Cook was a British astronomer.
 She joined the British Astronomical Association in 1911, and was elected a Fellow of the Royal Astronomical Society in 1916, part of the first group of women elected as fellows.
 She was renowned for her work observing meteors, and also observed naked-eye phenomena including the zodiacal light and aurorae.
 During World War One Cook, with Fiammetta Wilson, headed the British Astronomical Association's Meteor Section.
 Cook observed comets and Milky Way novae and was among the discoverers of V603 Aquilae, a nova that occurred in 1918.
 This work earned her the Edward C. Pickering Fellowship from the Maria Mitchell Association in 1920–1921.
 From 1921 to 1923 Cook was sole director of the British Astronomical Association's Meteor Section.
 With Joseph Alfred Hardcastle, Cook worked to identify and describe 785 New General Catalogue objects on a series of photographic plates taken by John Franklin-Adams.
Professor David Flower is a British astronomer and physical chemist and the current Editor in Chief of the Monthly Notices of the Royal Astronomical Society (MNRAS).
 He is an Emeritus Professor in the Durham University Department of Physics.
 He became Editor in Chief after a long term as an MNRAS editorial board member.
 He is a Fellow of the Royal Astronomical Society, and a Fellow of the Royal Society of Arts.
Isabel Martin Lewis (July 11, 1881 – July 31, 1966) was an American astronomer who was the first woman hired by the United States Naval Observatory as assistant astronomer.
 In 1918, Lewis was elected a member of the American Astronomical Society.
 She was also a member of the Royal Astronomical Society of Canada and the Astronomical Society of the Pacific.
Richard Huziak (born March 18, 1957 in Yorkton, Saskatchewan) is a Canadian amateur astronomer for whom the International Astronomical Union named main-belt asteroid 4143 Huziak.
 A former president of the Royal Astronomical Society of Canada Saskatoon Centre for six years and a prominent member of the American Association of Variable Star Observers, Huziak has over 165,000 observations of variable stars to his credit.
 He received the Chant Medal from the Royal Astronomical Society of Canada in 2001, the Service Medal from the same organization in 2009, and Janet Mattei presented Huziak with the AAVSO's Director's Award in 2003.
The Royal Astronomical Society (RAS) is a learned society that began as the Astronomical Society of London in 1820 to support astronomical research (mainly carried on at the time by 'gentleman astronomers' rather than professionals).
 It became the Royal Astronomical Society in 1831 on receiving its Royal Charter from William IV.
 A Supplemental Charter in 1915 opened up the fellowship to women.
 It is the UK adhering organisation to the International Astronomical Union and a member of the Science Council, and encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.
 Meetings are held in Burlington House, in Piccadilly, London and across the United Kingdom (UK).
 They are involved in the production of astronomical journals and periodicals.
 The society has over 3000 members, around a third of whom live outside the UK.
 In addition, those members of the public who have an interest in astronomy and geophysics and wish to support the work of the society may become Friends of the RAS.

Question: John Henry Reynolds was a British astronomer who served as the president of the Royal Astronomical Society who frequently corresponded with American astronomer Edwin Hubble, developed a formula for measuring the surface brightness of what? 
Answer: elliptical galaxies