**Donald Sadler** was a mathematical astronomer who spent his career working at the Nautical Almanac Office. He made major contributions to the construction of mathematical tables. He served as President of the Royal Astronomical Society and worked tirelessly for international collaboration.

- James and Gertrude' first son, Cyril Arthur Needham Sadler, was born in Lincoln on 1 December 1904 and baptised in Loughborough on 21 May 1905.
- After attending primary school in Dewsbury, Donald entered the Wheelwright Grammar School in Dewsbury which had been founded and endowed in 1724 in the will of John Wheelwright.
- When Sadler began his studies at the school in 1919 the headmaster was Leslie Sadler.
- (Despite being a 'Sadler' they were not related).
- Leslie Sadler was a fine teacher and an excellent mathematician who had gained a double first class degree in mathematics and physics at Oxford University.
- He had a strong influence on Donald, encouraging him in his study of mathematics.
- This inspiring teaching helped Donald to win an Open Scholarship to Trinity College Cambridge in 1926.
- Among Sadler's fellow students, there were a number of outstanding mathematicians including Donald Coxeter, Patrick Du Val and Harold Davenport.
- Sadler was first class in Part 1 of the Mathematical Tripos since his performance in the second year examinations was outstanding, he was awarded a Senior Scholarship.
- Sadler avoided physics courses since he had not studied any advanced physics at the Wheelwright Grammar School but did take astronomy courses such as Frederick Stratton's spherical astronomy.
- Sadler also took courses on orbit calculation and celestial mechanics given by William Smart, a lecturer in mathematics and the John Couch Adams Astronomer.
- Sadler was First Class in Part 2 of the Mathematical Tripos in 1929 and, since his scholarship was for four years, decided to remain for another year.
- During this fourth year at Cambridge, Sadler began to look for a job.
- William Smart, one of Sadler's lecturers at Cambridge, suggested to Comrie that Sadler would be a good person to appoint to the Nautical Almanac Office.
- Sadler received an invitation to attend for interview for a post and was offered a position as Temporary Assistant to Comrie which he accepted, beginning work on 13 October 1930.
- Sadler learnt much from Comrie and was appointed Deputy Superintendent in 1933.
- Admiralty: Senior Assistant in the Nautical Almanac Office, Donald Harry Sadler.
- There were, however, tensions between Comrie and his superiors regarding his use of machines for calculation and taking on outside work, and he was suspended at short notice on 19 August 1936; Sadler became Acting Superintendent.
- We were allocated a few rooms in the College, D H Sadler in a room overlooking the river and the majority of staff in one large room ...
- Sadler began publishing soon after taking up his position at the Nautical Almanac Office in 1930 and took over several projects which Comrie had been working on.
- Harold Spencer Jones (1890-1960) was the Astronomer Royal of England at this time and Sadler became his assistant.
- On 27 July 1937 Sadler was appointed Superintendent of the Nautical Almanac Office.
- In 1938 Sadler published the paper New Geometry for Germany in which he discussed Germany's intention to make geometry decimal with 100 degrees to a right angle.
- D H Sadler was suddenly responsible for all his very young and junior staff.
- Donald Sadler, Comrie's successor as Superintendent, began to take on outside work in autumn 1939.
- However, it was not until July 1941 that Sadler received an extra member of staff to help cope with the ever increasing work load.
- Because of Sadler's unique position in running a major computing facility to which many service ministries were applying for help, he could see a need for a large, central computing facility to which all of the armed forces and the scientific civil service could have access.
- For his contribution to the war effort, Sadler was awarded an OBE in 1948 and, in the same year, the US Institute of Navigation gave him their Thurlow Award.
- We should at this point mention the excellent service that Sadler gave to the Royal Astronomical Society.
- Donald Sadler, the Superintendent, then carried through the unification of the almanacs of the UK and the USA.
- Sadler had been aiming even higher - for an 'International Astronomical Ephemeris', but he did not achieve this, although Germany gave up its 'Astronomisches Jahrbuch' and took over from us the work of publishing 'Apparent Places of Fundamental Stars'.
- The unification of the 'Nautical' and 'Air Almanacs' was accompanied by a unification of the auxiliary navigation tables and Sadler played a major role in this.
- Born in Aberdeen, Scotland, on 4 June 1912, Flora had been awarded an Honours Degree in mathematics and physics from the University of Aberdeen in 1934, became a lecturer in applied mathematics and, in 1937, joined the Nautical Almanac Office soon after Sadler had become Superintendent.
- Early in 1970, Sadler was released from his duties as Superintendent at the Nautical Almanac Office so that he could plan the International Astronomical Union General Assembly that was to be held at the University of Sussex in August of that year.
- The bond that D H Sadler created between himself and his staff remained until his death, as was very obvious when old staff returned from near and far.
- Although he made no major scientific discovery, Sadler contributed a great deal to astronomy and navigation, and it is probable that other fields of science have benefited from his diverse activities, particularly in the publication of mathematical tables.
- Sadler suffered from angina, and he died at his home, 8 Collington Rise, Bexhill, Sussex.

Born in Aberdeen, Scotland, on 4 June 1912, Flora had been awarded an Honours Degree in mathematics and physics from the University of Aberdeen in 1934, became a lecturer in applied mathematics and, in 1937, joined the Nautical Almanac Office soon after Sadler had become Superintendent. * Early in 1970, Sadler was released from his duties as Superintendent at the Nautical Almanac Office so that he could plan the International Astronomical Union General Assembly that was to be held at the University of Sussex in August of that year. * The bond that D H Sadler created between himself and his staff remained until his death, as was very obvious when old staff returned from near and far. * Although he made no major scientific discovery, Sadler contributed a great deal to astronomy and navigation, and it is probable that other fields of science have benefited from his diverse activities, particularly in the publication of mathematical tables. * Sadler suffered from angina, and he died at his home, 8 Collington Rise, Bexhill, Sussex.

Born in Aberdeen, Scotland, on 4 June 1912, Flora had been awarded an Honours Degree in mathematics and physics from the University of Aberdeen in 1934, became a lecturer in applied mathematics and, in 1937, joined the Nautical Almanac Office soon after Sadler had become Superintendent. * Early in 1970, Sadler was released from his duties as Superintendent at the Nautical Almanac Office so that he could plan the International Astronomical Union General Assembly that was to be held at the University of Sussex in August of that year. * The bond that D H Sadler created between himself and his staff remained until his death, as was very obvious when old staff returned from near and far. * Although he made no major scientific discovery, Sadler contributed a great deal to astronomy and navigation, and it is probable that other fields of science have benefited from his diverse activities, particularly in the publication of mathematical tables. * Sadler suffered from angina, and he died at his home, 8 Collington Rise, Bexhill, Sussex.

Born 22 August 1908, Dewsbury, Yorkshire, England. Died 24 October 1987, Bexhill, Sussex, England.

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Astronomy, Origin England

**Oâ€™Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive