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

The Sundial Primer Index

Dialling with QBASIC - Mac Oglesby - Equation of Time

The QBASIC routines presented here will provide the Equation of Time in either table or graph format.

Equation of Time Table - Eottbl05.bas

"Here's a little QB program that I've used a lot. It generates a table of EoT values (only), or EoT plus the usual longitudinal offset, or EoT plus Longitude offset plus daylight saving."

You can get the QBASIC program as well as three sample text files here.

Figure 1 shows the program when it is opened in QBASIC. Normally the writer will provide comments about and instructions of how to use  the program that are very useful. It is always a good idea to read at least the beginning of the program.

Figure 1: Equation of Time Table QBASIC Program

Figure 1: Equation of Time Table QBASIC Program

The program can be run by pressing "F5". Figure 2 shows the dialogue this program goes through. You can type in the location and name of the text file that will be created if you do not wish to use the default. If the default directory "basic" does not exist an error message will be given and it is necessary to exit QBASIC and start again. The program also asks for a couple of longitude values.

Figure 2: Equation of Time Table Dialogue Screen

Figure 2: Equation of Time Table Dialogue Screen

Figure 3 is a screen capture of the table as it is displayed when the program completes its run.

Figure 3: Equation of Time Table Output Screen

Figure 3: Equation of Time Table Output Screen

Equation of Time Graph - Eotgraf5.bas

"Here's another QB program I've found useful. It was this program which helped me create the EoT graph on the shadow plane dial. When run, the screen has a lot of information.

his zip has the program and a DeltaCad file of the output, after the txt file was processed to a dxf by CNVXXXX.EXE. The large cross at the left edge of the graph is put there by CNVXXXX to mark the drawing's origin (0,0). As to labeling the drawing, the bottom line is 32 minutes and the top is 66, info which was on the DOS screen. The months are Jan through Dec, left to right, with the vertical lines marking the 1st, 11th and 21st of each month."

You can get the QBASIC program as well as the DeltaDad file here.

This program follows what was discussed above. Figure 4 shows the screen capture of the graph.

Figure 4: Equation of Time Graph Output Screen

Figure 4: Equation of Time Graph Output Screen

Figure 5 shows the same graph but after the text file was converted to a DXF file using CNVxxxx and it was opened in DeltaCad.

Figure 5: Equation of Time Graph in DeltaCad

Figure 5: Equation of Time Graph in DeltaCad

"There are lots of EoT programs around, but my reason for writing my own was to get exactly what I wanted. Actually, I find the EoT table more useful because few of the general public are willing to take the time to puzzle out a graph. I guess I've stopped putting EoT graphs on my dials, although they make a prettier decoration than a table."