 After returning to Ellicott's Mills, Banneker made astronomical calculations that predicted eclipses and planetary conjunctions for inclusion in an almanac and ephemeris for the year of 1792.To aid Banneker in his efforts to have his almanac published, Andrew Ellicott (who had been authoring almanacs and ephemerides of his own since 1780) forwarded Banneker's ephemeris to James Pemberton, the president of the Pennsylvania Society for Promoting the Abolition of Slavery and for the Relief of Free Negroes Unlawfully Held in Bondage.Pemberton then asked William Waring, a Philadelphia mathematician and ephemeris calculator, and David Rittenhouse, a prominent American astronomer, almanac author, surveyor and scientific instrument maker who was at the time serving as the president of the American Philosophical Society, to confirm the accuracy of Banneker's work.