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

The Sundial Primer Index

DeltaCad Sundial Macros - Ron Anthony

Ron Anthony wrote a number of DeltaCad macros that can be used to generate horizontal sundials. There are a total of 7 macros that will be discussed and you can get them all here. The default values are used in the cases where user input is required. These macros will illustrate the development a horizontal sundial macro from a simple form to one that allows the user a great deal of control over the design of the sundial.

The design of the gnomon is left to the user but is not difficult. Remember that the style height, in degrees, for a horizontal sundial is equal to the latitude of the sundial's location.

Horizontal Sundial 1

This horizontal sundial is automatically generated and the drawing  is shown in Figure 1. This macro draws a sundial for the Northern Hemisphere at a latitude of 38.75. It indicates local apparent or solar time and only draws the hour lines for the full hours. It is intended to illustrate the code for a simple horizontal sundial.

Figure 1: Horizontal Sundial 1

Figure 1: Horizontal Sundial 1

What if you want to draw a sundial for a different latitude? It is possible with this macro. By selecting the "E" button the macro can be opened for editing as shown in Figure 2. Notice this line near the bottom: "Latitude = 38.75". This value can be changed to a new latitude, the macro saved and run again to generate a different sundial. A positive latitude results in a sundial for the Northern Hemisphere and a negative latitude a sundial for the Southern Hemisphere.

Figure 2: Horizontal Sundial 1 Macro

Figure 2: Horizontal Sundial 1 Macro

This doesn't seem like a lot of fun so let's move on to the next sundial macro.

Horizontal Sundial 2

This horizontal sundial is generated after the user enters the "Latitude" of the sundial's location as shown in Figure 3. A positive latitude results in a sundial for the Northern Hemisphere and a negative latitude a sundial for the Southern Hemisphere. The drawing is similar to that shown in Figure 1.

Figure 3: Horizontal Sundial 2 Macro

Figure 3: Horizontal Sundial 2 Macro

Horizontal Sundial 3

This horizontal sundial is generated after the user enters the "Latitude". "Longitude" and "Timezone" of the sundial's location as shown in Figure 4. Follow the sign convention carefully. Positive and negative latitudes are accepted.

Figure 4: Horizontal Sundial 3 Macro

Figure 4: Horizontal Sundial 3 Macro

The sundial drawn with this macro is shown in Figure 5. Notice the hour lines are slightly rotated. The hour lines for this sundial have been corrected for longitude and indicate zonal solar time.

Figure 5: Horizontal Sundial 3

Figure 5: Horizontal Sundial 3

Horizontal Sundial 4

This horizontal sundial is generated after the user enters the "Latitude". "Longitude" and "Timezone" of the sundial's location as shown in Figure 4. The only change that has occurred is that the sundial now has a border that bounds the hour lines.

Figure 6: Horizontal Sundial 4

Figure 6: Horizontal Sundial 4

Horizontal Sundial 5

This horizontal sundial is generated after the user enters the "Latitude". "Longitude" and "Timezone" of the sundial's location as shown in Figure 4. This sundial has the added feature of declination lines for the solstices and equinoxes. The declination lines are drawn assuming a pin gnomon located where the small red circle is shown. This location does not change with latitude and results in the upper solstice line moving off the dial plate at higher latitudes.

Figure 7: Horizontal Sundial 5

Figure 7: Horizontal Sundial 5

Horizontal Sundial 6

This horizontal sundial is generated after the user enters the "Latitude". "Longitude" and "Timezone" of the sundial's location as shown in Figure 4. This sundial also compensates for a thick gnomon with a fixed width of 1/4-inch. Notice the sundial has two centres and the hour lines originate from one of these depending upon the time of day. Also the two solstice lines are split at their centres by the width of the gnomon.

Figure 8: Horizontal Sundial 6

Figure 8: Horizontal Sundial 6

Horizontal Sundial 7

This horizontal sundial is generated after the user enters a number of variables as shown in Figure 9. There are 3 main areas where information can be entered to define the characteristics of the sundial. These are "Location", "Dimensions" and "Features". Read the "Help" window for each of these areas carefully to fully understand what each of these variables defines. When all the required entries are made select the "Draw Dial" button and the sundial will be drawn. Once the sundial appears select the "Exit to DeltaCad" button.

Figure 9: Horizontal Sundial 7 Macro

Figure 9: Horizontal Sundial 7 Macro

Figure 10 illustrates the horizontal sundial generated with the above values for the variables.

Figure 10: Horizontal Sundial 7

Figure 10: Horizontal Sundial 7

Vertical Direct North/South Sundial

If you would like to design a vertical direct south sundial for the Northern Hemisphere or a vertical direct north sundial for the Southern Hemisphere it is possible to do just that with the horizontal sundial macro. The important fact to remember is that a vertical sundial at a specific latitude is equivalent to a horizontal sundial at the co-latitude of the opposite hemisphere. To design a vertical sundial for 50 N first design a horizontal sundial for the co-latitude 40 but in the Southern Hemisphere. Rotate the entire sundial by 180 to orientate it as a vertical sundial. Remove the hour lines and numbers before 6 a.m. and after 6 p.m. local apparent or solar time. Rotate the remaining hour numbers by 180. The vertical sundial is complete and will appear as shown in Figure 11.

Figure 11: Vertical Direct South Sundial - Northern Hemisphere

Figure 11: Vertical Direct South Sundial - Northern Hemisphere

Remember that the style height, in degrees, for a vertical sundial is equal to the co-latitude of the sundial's location.


Vertical Sundial 4

The name of this sundial is the result of the fact that the macro is derived from the Horizontal Sundial 4 macro. The modifications required to produce this macro were written by Peter Mayer. It can be used to draw a vertical direct north/south sundial.

This vertical sundial is generated after the user enters the "Latitude". "Longitude" and "Timezone" of the sundial's location as shown in Figure 4. The sundial shown in Figure 12 uses the default values and is actually for the Southern Hemisphere.

Figure 12: Vertical Direct South Sundial - Southern Hemisphere

Figure 12: Vertical Direct South Sundial - Southern Hemisphere

Note that any hour lines above a horizontal line passing through the sundial's origin need not be included. The vertical direct north/south sundial will not be illuminated during those times.