Beyer's observations of Mars. Six dated and labelled observations of Mars made during the opposition of 1924 by M. Beyer of the Hamburg Bergedorf Observatory, Germany. An opposition is the point where a planet is closest to Earth during its orbit around the Sun. Beyer observed distinctive features on Mars, such as Sinus Sabaeus, Syrthis Major and the polar caps. However, he failed to see the Martian 'canals' that the US astronomer Percival Lowell had claimed existed. It is now accepted that these 'canals' were an optical illusion.