The angles z of the hour lines are computed by the formula: tan(z) = sin(φ) · tan(τ+∆φ) φ = latitude, τ = hour angle, τ=n·15°, ∆φ is the deviation from the time zone meridian Instructions Choose your location from the menu, or: enter (in decimal degrees) your latitude (southern negative), enter (in decimal degrees) your longitude (western negative),         then hit the button "Apply input" Adjust the timezone offset Check the box "Insert Gnomon" Select "Show Hours" from the Details menu Copy the left pie circle by a screen capture tool and print Cut away the indicated sector Fold up the gnomon and glue the two halves together Set it up on a horizontal plane, the gnomon pointing to North (or South) Example: 51,5° North und 8° East 0n 2002, September 29 at 15:50 CEST The equation of time is about + 10 minutes, the sundial is fast at this amount. This sundial is made of brass: