365 Days of the Moon -- August 11, 2014

Bailly



      Last Saturday night, most lunar observers were enjoying the perigee full moon, hyped in the press as the "Supermoon". While I also enjoyed this
      natural curiosity, I was more excited by the fact that the south Texas seeing was calm enough to allow boosting my telescope to 7000mm focal
      length for the first time in months. Thus while others were imaging the full moon, I was marching up and down the thin terminator of the 98%
      illuminated Moon.

      In this view we are looking at Bailly, a relic from the Nectrian Epoch that is the largest crater on the near side of the Moon that hardly anyone
      knows about. Tucked into the south-southwest limb of the Moon, Bailly spans an amazing 183 miles across, but its location near the edge of the  
      visible moon severely foreshortens this massive crater and most novice observers do not notice it. Since it exceeds 300 kilometers in diameter, 
      I argue that Bailly should technically be considered a basin, not a crater.

      Last Saturday's "Supermoon" coincided with a good libration that pushed Bailly further into our view and allowed us to see the entire span of the
      crater and slightly beyond. The rough mountainous bump extending into the darkness to the right of Bailly is part of the ruined crater Le Gentil.

Image taken through a Celestron 11 Edge HD, 2.5X Powermate, and Skyris 274M camera.


Image copyright Robert Reeves 2014


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