Capricorn: Dec.22-Jan.29 The Sundial Primer
created by Carl Sabanski
Capricorn: Dec.22-Jan.29

The Sundial Primer Index

DeltaCad Sundial Macros - Fer de Vries

Fer de Vries wrote a couple of DeltaCad macros that can be used to generate nomographs of the sun's azimuth relative to the time and date. The nomograph can be used to build an azimuth sundial.

Azimuth Nomograph 1 - Az-Nomograph

This nomograph is generated after the user enters the "Latitude", "Local meridian" and "Zone meridian" of the their location as shown in Figure 1. The nomograph is corrected for longitude as required and can also be corrected for the Equation of Time by entering 1 for the "EoT". The "Month on top" controls whether the nomograph starts from January or July and will affect how it appears when drawn.

Figure 1: Nomograph 1 Macro

Figure 1: Nomograph 1 Macro

Figure 2 displays the nomograph as it would appear with the entries in Figure 1. The hour lines are corrected for longitude and the EoT and indicate standard time. The hour lines are numbered for standard time at the top and daylight saving time at the bottom. The months are displayed on the vertical axis and the sun's azimuth on the horizontal. The sun's azimuth can be easily determine for any time and day of the year. First draw a horizontal line for the desired date using the two date scales to align the ruler. Find the point where this line crossed the time that the sun's azimuth is to be found. Draw a perpendicular line from this point until it crosses one of the azimuth scales. Read the sun's azimuth at this point. 0 indicates the sun is directly south. Positive values are west and negative values east. As the hour lines indicate clock time it is easy to find the correct hour line.

Figure 2: Nomograph 1

Figure 2: Nomograph 1

Azimuth Cylinder Sundial

It is possible to use this nomograph to create a azimuth cylinder sundial. First determine the circumference of the cylinder to be used. This could be a cardboard tube or a plastic pipe for example. The nomograph is rescaled so the length of the azimuth scale is equal to the circumference of the cylinder. When wrapped around the cylinder the two lines indicating 180 and -180 must meet. With the nomograph as shown the date scales would be cut off. Move either the left date scale to the right of the 180 line or the right date scale to the left of the -180 line. Now when the nomograph is cut out it will be complete. Carefully glue it to the cylinder. The sundial is complete. Place the sundial in a sunny location and position the 0 azimuth line facing true west. Half the cylinder is always shaded and the time is read along the vertical line between the light and shade.

Mac Oglesby wrote a very informative set of notes on the macro Az-Nomograph. It includes examples of sundials created using the macro. There are also a number of DeltaCad drawing files provided for the sundials discussed.

Notes on Az-Nomograph

Azimuth Nomograph 2 - Az-Nomograph-Plus-Bab-It

This nomograph is generated after the user enters the same information requested in Figure 1. Figure 3 displays the nomograph as it would appear with the entries in Figure 1. After the nomograph is drawn it first appears as in Figure 2. Select the "View" tab and then the "Layer" button.  Turn off all the "Normal" layers and turn on all the "Bab" layers. The nomograph will show Babylonian hours as drawn in Figure 3. Now turn off all the "Bab" layers and turn on all the "It" layers. The nomograph will show Italian hours as drawn in Figure 4.

Figure 3: Nomograph 2 - Babylonian Hours

Figure 3: Nomograph 2 - Babylonian Hours

Figure 4: Nomograph 2 - Italian Hours

Figure 4: Nomograph 2 - Italian Hours

The Italian Hours nomograph can be used to create an "Hours Til Sunset" Azimuth Cylinder sundial.