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

The Sundial Primer Index

DeltaCad Sundial Macros - Valentin Hristov - Horizontal Box Altitude Sundial

This macro draws a sundial that indicates the time using the sun's altitude (elevation, height).

Valentin has also created a macro for this sundial that uses two separate boxes with a common gnomon.

Horizontal Double Box Altitude Sundial

Horizontal Box Altitude Sundial - sdboxh

This box sundial is generated after the user enters the "Latitude", "Longitude" and "Central meridian" of the sundial's location as shown in Figure 1. A "Place" descriptor can also be included. Hour lines intervals of 15 and 30 minutes and one hour are available. The hour lines can be adjusted for longitude and the Equation of Time. Longitude correction can be removed by entering the same value for "Longitude" and "Central meridian".

Figure 1 - Horizontal Box Altitude Sundial Macro

Figure 1 - Horizontal Box Altitude Sundial Macro

The sundial drawn with this macro is shown in Figure 2. 

Figure 2 - Horizontal Box Altitude Sundial

Figure 2 - Horizontal Box Altitude Sundial

Two sets of hour lines are drawn, one for the morning hours and one for the afternoon hours. Unfortunately, close to local noon the change in altitude is very small and it is practically impossible to determine the time with reasonable accuracy. There are two sets of hour numbers. The blue indicate standard time and the red indicate Daylight Saving time. Rotate the horizontal box until the arrow in the middle pointing to the smiling printed sun also points to the real sun (the arrow follows the azimuth of the sun). A convenient way to do this is to watch when the short sides of the box cast no shadows. The long edge of the box, with the sun, is then the shadow casting edge or style.

Figure 3 shows a photo of the completed sundial.

Figure 3 - Horizontal Box Altitude Sundial Model

Figure 3 - Horizontal Box Altitude Sundial Model

Horizontal Box Altitude Sundial: Monthly Edition - sdboxhm

This macro is similar to the one above except it has an additional entry for "Month" as shown in Figure 4. Only one month can be selected, "1" for January, "2" for February, "3" for March and so on. The box sundial drawing will be only for the selected month. This results in greater spacing between the hour lines and makes it easier to read the time.

igure 4: Horizontal Box Altitude Sundial:Monthly Edition Macro

Figure 4: Horizontal Box Altitude Sundial: Monthly Edition Macro

Figure 5 shows box sundials drawn for the months of March and June on the top and September and December on the bottom, i.e. the solstices and equinoxes.

Figure 5: Horizontal Box Altitude Sundials for March, June, September and December

Figure 5: Horizontal Box Altitude Sundials for March, June, September and December

Figure 6 compares the sundials created by "sdboxh" and "sdboxhm". Both images are for the morning hours and are drawn at the same scale.. On the left the month of September is bounded in green as drawn by "sdboxh". On the right is the same month as drawn by "sdboxhm". The entire vertical height is used for a single month. The hour lines are well defined and the time can be read with greater accuracy.

Figure 6: Comparison of "sdboxh" and "sdboxhm" for September

Figure 6: Comparison of "sdboxh" and "sdboxhm" for September

All you have to do is make 12 of these sundials, one for each month, which is not difficult to do. Then just carry the one for the appropriate month. Figure 7 shows 12 such sundials with January at the upper left the continuing to the right and December at the lower right.

Figure 7: A Year's Worth of Sundials

Figure 7: A Year's Worth of Sundials