ANY CALCULATOR     DECLINING VERTICAL SUNDIAL CALCULATOR
 Latitude Declination Wall angle Hour angle Length BC Length AB Shadow angle FCG Length AD Shadow length CF Length BD Horizontal dist' FG Length CD Vertical dist' CG Angle ACD To run another calculation, just edit in the blue panel as required. Angle BCD Only press reset to clear all boxes.
 A Few Notes Before you start carving one out of a solid block of marble, please test it out on a cardboard version first! All the information on this page applies to sundial design for the northern hemisphere. If you live in the southern hemisphere you will have to take account of the fact that the sun is north at noon, not south.. A book reference is "Sundials Their Theory and Construction" by Albert E.Waugh. It contains lots of information on the design and setting up of various types of sundial. Sundials are not accurate at all times of the year due to the effects of the equation of time, the error can be in excess of 16 minutes. It is however possible to design a sundial that should be accurate to within around 2 minutes throughout the year. This has traditionally taken the form of the noon dial called the Analemma. If the shadow cast by the tip of the gnomon, 'A' in the diagram, and cast on the dial face at 'F' was marked on the face on the hour by clock time for each day of the year, it would be seen to have made a distorted figure of eight shape. The position of point 'F' can be calculated for any day of the year by finding what the equation of time and declination of the sun is. Horizontal distance 'FG' and vertical distance 'CG' give the co-ordinates for the point. The equation of time is quoted in minutes. As each hour is entered in this calculator as multiples of 15 degrees, the equation of time in minutes (et) need dividing by 4 (60/15) to convert it to degrees, and adding to or subtracting from the hour, which would be 0 ± et, 15 ± et, 30 ± et etc. Things to be aware of...the appropriate wall angle is required for a noon Analemma (hour angle = 0) depending on whether point 'F' is plotted on the east or west face of the dial, and deciding when the equation of time is to be added or subtracted from the hour angle depends not only whether 'et' is fast or slow on clock time, but also whether the hour angle is on the east or west face of the dial.. Longitude correction should also be included.