On Sun, Oct 30, 2016 at 02:37:04PM +0000, Frank King wrote: ... > Almost the first task is to find > the centre and the axes. Clearly > you cannot fold a slate in half > and the traditional way to proceed > is to put a large sheet of paper > over the slate and crease it down > all round the rim. > > You then cut round the crease and > attempt to follow your procedure!
Wrap the slate with a reflective strip (smooth, shiny plastic? thin polished metal?). Playing around with a laser should find the focii. Completely off the top of my head and untried in any way :-) K --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
