Hi Walter, It is not possible to increase the dimension of a sundial to increase the precision of the reading and to reach the possibility to read intervals of time very small.
The reason is in the diameter of the Sun, because of which when the style goes away from the (horizontal) plane its shadow becomes more and more fuzzy and uncertain (penumbra) One can find easily that in a horizontal sundial for the latitude of 45 d., at noon, in the equinoxes, the width of the shadow of an infinitely thin style, is equal about to the movement of the same shadow in 1 minute (without optical systems) For hours different from noon, the distance between the extremity of the stylus and the shadow increases, provoking an increase of the dimension of the shadow itself. It is this the reason that prevents the construction of sundials with a precisions superior to around 1 m. With some artifices (shaped holes, shadow sharpeners, etc.) we can reach also a better precision ( maximum 10-20 sec) +++++++++++++++++++++++++++++++++++++++ For the problem of the attachments I agree completely with Mac Oglesby Often it is necessary to show an image or a sketch and we cannot wait, before showing it, to put it in a web site (moreover not all have an URL ! ) and, after to write to the list. If I don't mistake, a message longer then 20 or 24 kb is rejected by the Majordomo: this rule of the 20-24 kb must then be accepted by everybody, also from those people that don't have interest for these attachments. Gianni Ferrari Lat. 44o 39' N Long. 10o 55' E
