The rear of my house faces 76 degrees west of south, so the sun only shines on the wall from about 11:30 am until sunset.
Rather than putting a declining sundial on the wall, I have an “Hours until the sun sets” dial.
The mathematics were kindly provided by Mac Oglesby
The dial is made from blue Traffolite, with a stainless steel 50mm pin near the top right corner. The position of the tip of the shadow indicates the number of hours until sunset - is there still time to get the BBQ out?
In the picture, the shadow shows that there are about 4 hours 20 minutes until sunset
Interestingly, the dial is independent of British Summer Time, Longitude, and the Equation of Time.
