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 Foster-Lambert Sundial Kit

Foster-Lambert Sundial: a form of equatorial projection dial, with the projection arranged to produce a circular ring of equiangular hour points.


A little adjustment to the equations for a Foster-Lambert sundial will result in a date scale that is independent of latitude. Times are still read as points on a circle for a particular latitude. But now you can include circles 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.

This sundial comes in two versions. One indicates solar time and the second is designed so it can be adjusted to indicate standard time. Both versions come with two kinds of gnomon. One is a fixed gnomon that is made to work at a single latitude.  The other is an adjustable gnomon and can be set to any latitude in the range of 25 to 65. Just take your pick or make both.

Figure 1 shows the Kit that you will use to make your own universal solar time Foster-Lambert 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.

Figure 1: Universal Solar Time Foster-Lambert Sundial Kit

Figure 1: Universal Solar Time Foster-Lambert Sundial Kit (CAD)

We have made up two kits so that you can build a universal solar time Foster-Lambert 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 solar time version "Universal Solar Time Foster-Lambert Sundial Kit" just open the door that works for you.

Universal Solar Time Foster-Lambert Sundial  Kit - Northern Hemisphere Universal Solar Time Foster Lambert 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. Just set it on a level surface and align the arrow 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 sloped edge is positioned on the centre line. Find the circle for your latitude. Solar time is read at the point the gnomon's shadow crosses the circle.

Figure 2 shows the Kit that you will use to make your own universal standard time Foster-Lambert sundial.

Figure 2: Universal Standard Time Foster-Lambert Sundial Kit

Figure 2: Universal Standard Time Foster-Lambert Sundial Kit (CAD)

The dial plate consists of two parts. The stationary plate with the date scale is shown on the right. The rotating hour line plate is on the left. Because the hour lines are separated by equal intervals the hour line plate can be rotated to correct for both the Equation of Time and latitude. As the hour lines are drawn at 10 minute intervals a vernier scale is included to help adjust the correction to the nearest minute. Figure 3 illustrates the vernier scale and how to use it.

Figure 3: Universal Standard Time Foster-Lambert Sundial Vernier Scale

Figure 3: Universal Standard Time Foster-Lambert Sundial Vernier Scale (CAD)

We have made up two kits so that you can build a universal standard time Foster-Lambert 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 solar time version "Universal Standard Time Foster-Lambert Sundial Kit" just open the door that works for you.

Universal Standard Time Foster-Lambert Sundial  Kit - Northern Hemisphere Universal Standard Time Foster-Lambert Sundial  Kit - Southern Hemisphere
Northern Hemisphere Southern Hemisphere

The set up of this sundial is the same as described above for the solar time sundial. However, the corrections for the Equation of Time and longitude are done by rotating the hour line plate.

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

Universal Foster-Lambert Sundial

Happy Dialling!