What tool should be used to select the farthest distance visible around the horizon circle?

The appropriate tool for selecting the farthest distance visible around the horizon circle is facility marker charts. These charts are designed to represent various visual landmarks and markers within a specific area, which can help pilots assess visibility conditions in relation to their surroundings. By showing significant landmarks, facility marker charts enable pilots to gauge the effective range of visibility, which can be critical for safe navigation and decision-making.

Visibility measuring devices are indeed useful for determining current visibility conditions, but they provide a specific measurement rather than an overview of the farthest visible distances in a broader context. Weather radar typically focuses on precipitation and storm detection rather than visual distance. Flight planning software assists with overall navigation and planning but does not specifically designate visible distances around a pilot's horizon. Therefore, facility marker charts are the most suitable tool for this purpose.