Article of the month July

Mirror sundials 2

Last month, we saw how the pattern of a sundial with a reflective nodus can be easily derived by considering the orientation of the reflected pole style.
This month, we look at some practical examples of sundials in which mirrored sunlight tells the time.

First, a postcard of my own invention.
The actual pole style points to the north, and is 52 degrees out of the horizontal plane. A mirror tilted 26 degrees towards the south makes the reflected pole style point horizontally to the north.
A homogeneous pattern for the winter months will now appear on the card.
The picture shows a ray of sunshine for 9:00 and for 11:00.

Another possibility is a canted armillary sundial.
To make a complete reflected pole style, a number of mirrors are placed in a row.
The reflected sunlight falls into the band, or armilla.

A final example is of a vertical cone.
A homogeneous pattern results when the nodus is placed on the central axis, and the mirror is tilted 19 degrees.
As a result, the reflected pole style points straight up.
As described last month, a homogeneous pattern appears around this reflected pole style.

The left photograph shows the position of the sun at true noon, 12 hours local apparent time.
The photograph to the right shows the situation at 1345 LAT on the same date.
The photo below shows the tilted mirror nodus in detail.