A Low-Budget Observatory on an Old Castle Site
The building warrant of June 22, 1675, designated a site near the old castle on the highest ground in Greenwich Park and called for working and living accommodation for the astronomical observer and his assistant. Christopher Wren was to provide the design, while the Ordnance organized craftsmen, procurement, and payment. Funds came from the sale of deteriorated gunpowder, and the warrant capped expenditure at £500. The Royal Observatory thus drew on existing royal land and Ordnance administration rather than a newly established large research budget.
Hyde Park and Chelsea College had previously been considered. Wren favored the hilltop at Greenwich: it was removed from London’s smoke and allowed the Thames to be used for transport. Construction employed timber from a demolished gatehouse at the Tower of London, together with bricks, iron, lead, and other materials from Tilbury Fort. The foundation stone was laid on August 10, 1675, but Flamsteed did not move in until July 10, 1676. These month-and-day dates follow the Old Style used in the sources. Appointment, the order to build, the laying of the foundation stone, and taking up residence were four distinct stages.
A Royal Building with Private Instruments
Completion of the building did not mean that equipment and staff were already fully provided. Early instruments depended on gifts and loans from Sir Jonas Moore, with some limited assistance from the Royal Society. In a later explanation of instrument ownership, Flamsteed listed a sextant and two clocks given by Moore and mentioned a micrometer given by Richard Towneley. Instruments, timekeeping devices, and the observing site had to work together to turn what was seen through a telescope into comparable records of position.
After Moore’s death, the ownership of equipment became the subject of a dispute with his heirs. In 1683, Flamsteed made a mural quadrant with a radius of fifty inches. Abraham Sharp subsequently assisted with precision instrument making and calculation, graduating a new mural arc with a seven-foot radius and an angular range of 140 degrees, which entered use in December 1689. Improvements in equipment resulted from prolonged fundraising, manufacture, and calibration; later instruments cannot all be counted as part of the original provision of 1675.
References: [1]
Recording Errors Alongside Measurements
A letter to Moore dated July 27, 1676, offers a detailed glimpse of early work. Flamsteed was measuring the Sun’s altitude in the morning to correct the timing of the previous night’s observations when he noticed prominent sunspots. He recorded the time and the distances between the spots and the Sun’s limb, and drew their positions. He also explained that wind shook the telescope tube and prevented further measurements, so some calculations used a previously measured solar diameter.
The letter did not treat every number as an equally reliable direct reading. It distinguished measurements made on the spot, reused earlier values, and calculated results. A letter to Towneley that December discussed the spots’ reappearance; a letter to William Molyneux in 1684 included a diagram predicting a spot’s path across the solar disk. Correspondence connected Greenwich’s observations with other researchers while preserving the distinction between predictions and actual measurements.
References: [3]
From Observing Books to Public Data
Observations required assistants to perform calculations, as well as printing funds and publication arrangements. Flamsteed supplemented his income by taking pupils in mathematics and astronomy, among other means, and paid some instrument costs himself. Such private contributions beyond his government salary shaped his understanding of ownership of both equipment and results. When Newton visited in 1694, the need for reliable lunar observations also brought the observatory into a network of collaboration in theoretical calculation.
The questions of when data were sufficiently mature and who could decide to publish them later became sharply contentious. Prince George of Denmark supported a publication plan, the Royal Society and its system of visitation became involved, and a Historia Coelestis edited under Halley’s direction appeared in 1712. Flamsteed rejected this edition and continued organizing his own work of revision. The episode involved cooperation among researchers as well as still-unsettled boundaries between state support, private investment, and responsibility for publicly available results.
References: [1]
The Value of Records Depends on How They Are Read
These observations served not only contemporary star catalogues; they also later became evidence for the study of solar activity. After examining Flamsteed’s correspondence, Carrasco and Vaquero pointed out that the absence of any mention of sunspots in a measurement of the Sun’s position cannot simply be counted as evidence that there were no spots that day. An explicit report of no sunspots must be distinguished from a record that says nothing about them. The lasting value of an early observatory lay both in its continuing production of numerical records and in its preservation of dates, instruments, weather, measurement purposes, and the context of correspondence, allowing later readers to reassess the limits of the evidence.
References: [4]