created by Carl Sabanski
Declination of a wall (d, DEC): the angle, measured in a horizontal plane, that a wall's perpendicular makes with due south (i.e. a wall facing S has d=0°). Walls declining westward have positive declinations, those eastward, negative. This is not a universal convention and some authors define the angle with respect to the nearest cardinal point of the compass.
If you want to build a vertical sundial on a wall that does not face directly south, east or west you will need to determine the declination of this wall before starting your design. There are various methods available to do this that require a lot of calculation or the use of software. The Solar Noon Window "Wall Declinometer" will give you a direct reading of the wall declination. No calculations are required!
Sure this is a simple device but there is one drawback. You can only take a reading once a day....at solar noon. But you can do this while you are thinking about the other details of your sundial. So what's a few extra days? Nothing!
Once you have made all the parts all you have to do is assemble it on the outside of any window. It's best if you put it on a window located on the wall that is of interest. You will need an accurate digital clock and the time for solar noon at your location. Remember that this is the time the sun passes over your local meridian and does not include corrections for longitude and the Equation of Time. A software program like "The Dialists Companion" can help you to determine this time.
Figure 1 illustrates the template for the "Wall Declinometer". It is easy to build!
Figure 1: "Wall Declinometer" (CAD)
If you would like to have the "Wall Declinometer" you can download a pdf file of a kit that you can put together. It includes the instructions for assembly. The construction materials are only suggestions and you can build the device from anything you would like to use.
that this "Wall Declinometer" is mounted on the wrong side