Comprises handwritten, indexed notebook on the theory and practice for the reduction of observations made with the Herstmonceux Astrolabe (OPL 9). The notebook is labelled 'R. Wallis'.

Subjects include: developing and reading films; data cards; runs Z, A, M and N; weekly routine; position of Astrolabe; drawing the solution; obtaining GBR/UTO; weights and latitude; weekly sheets; test packs; instrument; observed zenith distance; corrections; equations; solutions weighting; least square methods. The volume contains a strip of film and computer punch cards.