  The principal elements of Gassendi's astronomy include a global embrace of empirical method, advanced instrumentation, and measurement, an interest in unusual celestial phenomena, and a partially masked defense of Copernicanism. His embrace of an empiricist astronomy can be gauged by his voluminous recorded observations—some presumably with the telescope lenses sent by his friend Galileo—carried out in concert with a league of fellow observers strung across Europe and the Near East. A primary goal of these recorded observations was to confirm and extend the Rudolphine Tables, the project set up by Tycho Brahe and completed by Kepler, to facilitate calculation of the planet's positions (which goal in itself suggests Gassendi's adherence to a Keplerian heliocentrism). Another facet of Gassendi's empiricist astronomy was his denunciation of astrology as crafted independent of any ideas from the senses, impervious to correction by experiment or observation, and thus as failing to qualify as natural or experiential knowledge.  This view brought him into direct and bitter conflict with Jean-Baptiste Morin, who also suspected Gassendi of an arch-Copernicanism that was not only against Church teaching but would obviate the astrological structures central to Morin's theories. Gassendi's close interests in observation also led to employing the camera obscura to gauge variations in the apparent diameter of the moon—in accordance with its orbit of the Earth and the apparent diameter of the Sun. Further, in his work with Peiresc, Gassendi tackled the problem of determining longitude by reference to lunar eclipses, later working towards this goal with Claude Mellan on the first effort to chart the moon.