A large set of lantern slides originally held in two eight drawer wooden cabinets (only xx drawers were used). The sets were labelled 'C' [Clusters and nebulae (galactic objects], 'D' [Spectra], 'EG' [Galactic Objects] 'I' [Instruments], 'H' [Historical], 'S' [Planets] and 'T' [Time]. Each slide is numbered within its alphabetical sequence and this numbering system has been retained in the slide title here. Many slides have hand-written titles along the top edge.

Most of the photographs in the collection are of celestial bodies including the sun, moon, planets, minor planets, comets, meteors, double stars, nebulae, star clusters and star fields (series S). Series S also includes images from solar eclipse expeditions. There is also a large collection of images of galactic objects including clusters and nebulae (series C and EG). The series titled 'historical' is comprised mainly of photographs of engravings of buildings and instruments, but includes an early photograph of the Royal Observatory showing Flamsteed House, the entrance gate and clock, dated December 1955 (RGO 85/2/1/4/38). Series I is a large series of images of astronomical telescopes and other instruments, mainly at the ROG and RGO Herstmonceux.

The slides were compiled from various sources. Most were internally produced by the ROG/RGO with a small number from the Cape Observatory. Others have additional 'RAS' or 'PAL' (Royal Astronomical Society) numbers. These appear to be slides collated by the RAS as teaching collections and sold commercially. From the early 1880s the RAS Photographic Committee curated and collected the best astronomical images from observatories and astronomers throughout the world. The RAS sale collection catalogue lists were produced semi-regularly until 1971. Additional information on such slides has been extracted from these catalogues to enhance the descriptions here.

The RAS slides in this collection include images from various international observatories including Lick Observatory, Mount Wilson Observatory, Yerkes Observatory, Palomar Observatory. Astronomers who took the photographs include E.E. Barnard, George Ellery Hale, Max Wolf, John Evershed, Ralph Hamilton Curtis, William Hammond Wright, J. Franklin-Adams.

Most slides are numbered and titled. Additional descriptive information was transcribed from the card catalogue, now at RGO 85/2/1/9.