Article of the month July

A surface, first horizontal and then rotated around a pole style, makes visible the principle of Babylonian and Italian hours.
Mac Oglesby made several sundial models that illustrate this, and one is shown here.

A wooden cylinder intersects a horizontal base at an angle equal to the latitude.
Around the lower part of the cylinder is a piece of plastic pipe. Its upper edge is in the equatorial plane.
On top of that is a second, rotating pipe, with a horizontal surface with a sight fixed to it.

This sight consists of a small hole for the sun to shine through, in as thin a sheet as possible.
The sunbeam falls on a surface with an index line parallel to the rotating surface.
Scales marked every 15 degrees, drawn on the rotating cylinders, let one read Babylonian and Italian hours.

The starting position for this sundial is with the upper surface horizontal. This is where Babylonian and Italian hours begin counting.
To read the sundial, one turns the top cylinder so that the sunbeam falls on the index line.
The time scales then show the actual Babylonian and Italian hours.

This model shows an hour scale for Italian hours marked as “hours until sunset”.
On the fixed part of the pipe is a second scale, which reads apparent solar time using the terminator on the cylinder.