Graphite on paper from books, dated from 1732-1840
The papers, drawn upon are from old books. Usually the first and the last pages. The celestial body drawn on each paper are the same amount of lighters away from us, as the paper is old. If a star is drawn on a paper from 1817, that means that the star is 200 lightyears away from us, and the light of the star we see today has been traveling towards us since the paper it is drawn on was made.