Moon tour Rupes Recta (Straight Wall)
If you have a small telescope, or a powerful pair of binoculars, and look to the lower left of the great triple-crater chain of Ptolemaeus, Alphonsus and Arzachel you will see – depending on the time of the month – either a short, dark line or a short, bright line. Moon atlases and phone apps identify it as ‘Rupes Recta’,
