Solar Decliner for Reverse Italian Hours

This web page creates a PDF file containing a design for a vertical "hours to sunset" solar decliner sundial. Two main configurations are possible:

The dial is assumed to be constructed from three uniform layers of transparent material (typically glass, air, glass). If fewer layers are used in your design, specify 0 for the thickness of the unwanted layers and 1 for their Refractive Index. For a non-refraction dial consisting of a simple peg gnomon in front of a dial face, specify a one-layer dial with your gnomon length as the layer thickness, use a Refractive Index of 1, and turn off the mirror setting.

Layer thicknesses (mm)Refractive Index
Latitude (degrees)For the Southern Henisphere, give the latitude as a positive number (you can reverse the finished image afterwards, if you wish).
Ratio of Dial Declination to Solar AzimuthUse this ratio to control the width of your dial face - it determines how far the dial must be declined for the equivalent solar azimuth. Please note that this web page does not check that the ratio is in an appropriate range. In particular, a refraction dial must be turned sufficiently to ensure that sunrays strike the faces, without excessive attenuation, even at summer solstice sunrises and sunsets. On the other hand, the higher the value the wider the resultant diagram. I recommend running the program a few times with different settings, until you find a value that produces a satisfactory layout.
Back surface is mirrored
Nodus diameter (mm)
Hour line width (mm)
Half hour line width (mm)
Quarter hour line width (mm)
Month line width (mm)
Ten day line width (mm)
Page width (mm)279 × 210 (or 210 × 279) is the magic size that just fits on both A4 and Letter.
Page height (mm)279 × 210 (or 210 × 279) is the magic size that just fits on both A4 and Letter.
Top margin (mm)

Mesh area is ? mm wide by ? mm high.

, 2017 - 2018. You are welcome to use the Javascript in this page either as is, or modified for your own purposes. Please retain comments acknowledging original authorship.

For an excellent source of general information on sundials, visit The North American Sundial Society.