17th Century Photometric Data in the Form of Johannes Hevelius's Telescopic Measurements of the Apparent Diameters of Stars

Johannes Hevelius’s 1662 Mercurius in Sole Visus Gedani contains a table of magnitudes and apparent telescopic diameters of nineteen stars. The data conform to a simple model, suggesting that Hevelius produced what is essentially a table of surprisingly precise photometric data.