CD sundial


	This portable dial makes a great gift, It can be setup to tell time any where in the Northern hemisphere. It adjust for longitude and latitude it comes with easy to follow instructions $25.00








	To order e-mail me dscott@igc.org and I will send a secure credit card invoice


		Refraction Sundial: phenomena discovered by M. Catamo & C. Lucarini in 1999, It has no gnomon, the shadow is replaced by bright line caused by the sun.




			www.gorissen.info/Pierre/maps/googleMapLocation.php stevemorse.org/jcal/latlon.php

		Both of the above sites will help find you find your longitude and latitude


		The latitude of my house is 42 deg. so that means I have to subtract 42 from 90. to get my co-latitude = 48 deg



	Each of the little diamonds at the bottom of the compass represent 5 degrees, they're used to correct the compass to true north


	The longitude correction depends on how far you are from the center of your time zone (the Meridian) Eastern 75,Central 90, Mountain 105 and Pacific is 120 degrees



			This equation of time graph is more common

http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp

The graph looks a little strange but it's essentially a rectangular graph like the one the right but its wrapped around the compass.

The vertical lines that radiate out from the compass are either the first or 15th of each month. the half circles are associated with the number of minutes to either add or subtract from the time on the sundial.

To use the graph

Find (guesstimate) today's date among the radiating lines, follow that position down and in until it intersects the wavy line, now follow that position around the circle to the scale on the bottom left.

that number is the value you will either add or subtract from the time on the dial face. You will have to guesstimate the number if the intersection point is in between two circular lines

For example find Feb. 1st; it intersects the wavy line in between the first and second circular line, if you follow it around the graph says to add something between 10 and 15 minutes to what ever time is on the dial

To Read the time on the dial

In the fall and winter the height of the sun (its azimuth) drops below the plane of the CD, sunlight hits the edge of the disk and the clear plastic acts as fiber optic cable and sending a slightly fainter line to tell the hour

in the summer you'll see a sharp, bright, line that radiates from the center of the CD that will be where you read the time, the drawing below explains what the lines mean. Remember your face should be directly in front of the disk

You will need to position your eyes directly in front of the CD, If you try reading it from an angle it will skew the time a bit. On a sunny day you will see a sharp bright line radiating from the center of the CD where that bright line crosses the lines on the dial face is where you will read the time

Again you will need to do a little estimating but.... well you get the picture

To best read the time,

center the reflection of your eye in the hole in the CD

This map shows the variation in magnetic intensity

One other factor that will effect the accuracy of the dial is the magnetic declination for your area, its caused by the earths magnetic poles, they really aren't located at the earths center of rotation. The amount of declination depends on where you are. It can easily be corrected for, on the compass. The link below will help you find the amount of correction to put on the compass setting when you aiming your sundial

http://www.ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml

again each of the little diamonds at the bottom of the compass represent 5 degrees, they're used to correct the compass to true north

The graph for this sundial is Fred Sawyer's rendering of a  little-known 19th century design  found in Bury St. Edmunds, England.

This Sundial base has been specially made for the 16th Annual Conference of the North American Sundial Society