Topography of the Alphonsus and Arzachel area of the Moon

Alphonsus (111km diameter) is one of the most intensively studied craters in the solar system, and has been a touchstone in lunar science throughout the past few decades. Its Dark Halo Craters (DHCs) have provided insights into lunar volcanism, particularly pyroclastic eruptions, while the area is notorious for its transient lunar phenomena including the seminal observations of an ‘eruption’ by Kozyrev in 1958. The crater was chosen in 1965 for the Ranger IX mission as a partial consequence of this activity (and in an effort to explore the highlands and basins as opposed to the mare of previous missions), and as a result was one of the first areas of the lunar surface to be imaged at high resolution. Amongst amateurs, it continues to be an observational favourite and target of high resolution astrophotography.

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