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

Mr. Sun The Sundial Primer Index "Sunny Day U" Index Mr. Sun

"SUNNY DAY U"


Universal Analemmatic Sundial Kit

Analemmatic Sundial: sundials consisting of hour points (rather than hour lines) laid round an ellipse, and a movable gnomon perpendicular to the dial plane. It may be on any plane, but the most usual form is horizontal. In the horizontal version of the dial, gnomon position lies on the straight North-South minor axis, at a point determined by the sun's declination (i.e. the date). The analemmatic dial may be regarded as a projection of the universal equatorial ring dial.


A little adjustment to the equations for an analemmatic sundial will result in a date scale that is independent of latitude. Times are still read as points on an ellipse for a particular latitude. But now you can include ellipses for a series of latitudes using the same date scale. The resulting sundial is now universal with a unique and interesting layout. It is also very easy to make.

Figure 1 shows the Kit that you will use to make your own universal analemmatic sundial. The dial plate of this sundial is designed to fit on an 8-1/2" by 11" sheet of paper.  It is purposely made as a large as possible to increase the resolution of the date scale and latitude lines.

Figure1: Universal Analemmatic Sundial Kit

Figure 1: Universal Analemmatic Sundial Kit (CAD)

We have made up two kits so that you can build a universal analemmatic sundial for the Northern or Southern Hemisphere. All you need are scissors, cardboard, glue and tape. If you would like to download a PDF file of the "Universal Analemmatic Sundial Kit" just open the door that works for you.

Universal Analemmatic Sundial  Kit - Northern Hemisphere Universal Analemmatic Sundial  Kit - Southern Hemisphere
Northern Hemisphere Southern Hemisphere

When you have completed the sundial all you have to do is set up and it will tell you solar time. All you have to do it set it on a level surface and align the arrows with your local meridian. i.e. the true north-south line.  If you are comparing the time to a clock remember to adjust the time for the Equation of Time and longitude correction. The "Correct-A-Dial" or "Correct-A-Dial II" will help you here. And if the clocks are set to summer time don't forget about the one hour (or whatever) difference.

When the sundial is correctly set up you must set the gnomon on the date line for the current date. The lines are spaced at 5 day intervals so you will have to estimate the correct position for certain days.  Make sure the gnomon's vertical edge is positioned on the centre line. Find the ellipse for your latitude. Solar time is read at the point the gnomon's shadow crosses the ellipse.

Here's what the sundial will look like once you have finished making it. This one is located in the Northern Hemisphere.

Universal Analemmatic Sundial

Happy Dialling!