Part of the Astronomer's Pocket Field Guide book series (ASTROPOC)


Ptolemaeus (93 miles) is a great circular formation a little south and just west of the center of the Moon. As the sun rises on this old giant at first quarter, long shadows are cast across the great expanse of the flat floor. Other than Ammonius, there are no sizable craters on the floor and it lacks any hills or crests. However, the floor is not without interest. Under low grazing illumination, you will notice several shallow, saucer shaped depressions. The largest of these depressions is directly north of Ammonius and has a diameter of about 10 miles. The great walls that surround the vast interior plain rise above the floor to more than 1½ miles in places. This old monster is a prize formation to show off to anyone at public observations. This formation will become one of your favorites, visible in any telescope and easily visible in 7 × 35 binoculars.


Circular Formation Great Wall Sizable Crater Flat Floor Public Observation 
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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.Louisville Astronomical SocietyLouisvilleUSA

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