A number of seriously interested amateur astronomers have tested the new Exodus refractor telescope. With it, they were able to observe in crisp detail planetary features that were seen only as fuzzy images in their 8-inch (approximately 20-centimeter) Newtonian telescopes, even though the 8-inch telescopes, with their wider apertures, gather more light than the 4-inch (approximately 10-centimeter) Exodus. Given these amateur astronomers' observational findings, any serious amateur astronomer ought to choose the Exodus if she or he is buying a telescope for planetary observation. The argument proceeds by ['supporting a recommendation to a group on the basis of the experience of a subset of that group', 'distinguishing between the actual reasons why a certain group did a particular thing and the best reasons for doing that thing', 'detailing the ways in which a testing situation approximates the conditions of ordinary use', 'placing a phenomenon in a wider context in order to explain it']