The BSS sundial glossary has the following entry under "Types of Dials":
"reflecting ~: these dials have no gnomon, but reflect sunlight by means of a semi-cylindrical mirror, set with the axis of the mirror parallel to the polar axis. The mirror reflects the light to form a caustic curve amongst the hour points. For the special case of the mirror having a cycloid shape, the hour points are equally spaced. Note that the term reflecting dial may also be used for ceiling dials." What is the typical dialface for a 'reflecting dial'? Are the comments above about semi-cylindrical mirrors apply equally to ceiling and wall dials? If a polar ceiling dial has an inclination of phi/2 what does having a mirror inclined at phi do? What is a caustic curve? David
