Telescope: 6-inch Franklin Adams wide-angle Star Camera (1898)

Commissioned by the Englishman John Franklin-Adams in 1898 and modified in about 1900, the 6-inch wide-angle Star Camera (focal length 27 inches) was lent to the Royal Observatory in December 1909 and subsequently purchased in 1912/13. It was mounted on the Thompson Equatorial in 1911/12, remaining there until at least 1914. In about 1965, it was mounted on the Astrographic Telescope in Dome C at Herstmonceux.

 

Early history

So successful was the 6-inch Camera, that Franklin Adams ordered a second camera with a larger 10-inch lens. Both cameras had a triplet lens made by Cooke to the designs of Dennis Taylor. Franklin-Adams used the two cameras to make a photographic survey of the skies, mounting them together with two 6-inch guiding telescopes on a single English Equatorial mount.

In 1902, Franklin-Adams became very unwell and was advised to travel to the Cape to recuperate. He decided he could use the opportunity to photograph the southern skies and had the telescopes shipped to the Cape Observatory in June 1903. He returned to England in 1904. In 1909, he decided to return to South Africa, but illness prevented him from going. The 10-inch camera was sent to the Observatory in Johannesburg under the charge of his assistant and the lens of the 6-inch camera loaned to the Astronomer Royal at Greenwich for use in photographing Halley’s Comet (which was due to reappear in 1910).

Between 1911 and 1914, three of the Greenwich Computers were employed to determine the number of stars of different magnitudes in the Franklin-Adams plates. The computers were: Entwistle (1911–12), Lambert (1911–12) and Perry (1913–14). The project was initially funded by Franklin-Adams, then jointly by him and the Royal Society. Adams died in 1912 and the Franklin Adams’s Chart of the Heavens published posthumously.

 

Use from 1911/12 onwards

Details of the use of the lens at the Observatory are rather sketchy. So far, it has been possible to establish the following:

In 1911/1912, the lens was mainly used for determining the photographic magnitudes of the bright stars in the Greenwich Astrographic Zone. In the annual report for 1912, Dyson explained:

‘It is necessary to supplement the photographs taken with the Astrographic telescope in this manner, because there are no stars brighter than 8m.8 sufficiently near the pole to serve as standards of comparison. This lens having a field which is sufficiently uniform over 3º radius, enables the whole zone to be completely observed by dividing it into 84 fields.’

In 1921/2, in an attempt to make ‘spectrophotometric observations of stars of different spectral types by means of an objective prism in conjunction with a wire grating, on the lines suggested by Prof. T. Merton’, an aluminium camera was constructed to carry the 6-inch Franklin Adams lens and a 7-inch prism of 40º angle.

In 1927, it appears to have been taken onboard HMS Fitzroy with the aim of using it to obtain photographs from the North Sea of the solar eclipse that was due to occur on 29 June. Click here to read more.

In 1965/6 when Woolley reported that:

‘Selected areas of the northern sky are being searched for variables by ‘blink’ comparison of plates taken with the 6-inch Franklin Adams wide-angle camera now installed in Dome C [on the Astrographic Telescope].’

Although it was still attached to the Astrographic Telescope in 1985 (see the 1980–85 annual report) it was subsequently removed. Its present whereabouts is unknown. The 10-inch Camera was presented by Franklin-Adams to the Transvaal (later the Union and now the South African Astronomical Observatory (SAAO)).

 

Contemporary Account

In 1904, the telescopes used in the Chart of the Heavens were described by Franklin-Adams, H. Dennis Taylor and Alfred Taylor in Monthly Notices of the Royal Astronomical Society, Vol. 64, pp.608–626.

 

Images

In his volume Greenwich Observatory (London, 1975), Howse included an RGO photograph (Fig.87) of the Astrographic Telescope at Herstmonceux to which the Franklin Adams Star Camera appears to be attached. The RGO archives in Cambridge hold the RGO negative collection (for which there is not currently an on-line catalogue).