ДОСВІД ВІДТВОРЕННЯ ПАРКОВОГО СОНЯЧНОГО ГОДИННИКА XVIII СТОРІЧЧЯ

This article describes the practical experience of the authors in studying the original artifact and producing a functional replica of the park sundial originally for the park near Hartlebury castle in Worcestershire, UK. The original sundial was produced around 1730 on the order of bishop John Hough by the mathematician John Dougharty. Since the original piece suffered damage from natural erosion and attempt of theft, some of its parts were missing and some of the scales were unreadable. Consequently the authors instead of making a cast opted to produce  first the theoretical model of the dial. The dial was redrawn in CAD-software and transferred to the brass plates through chemical etching. The missing elements were recreated using other contemporary samples. The dial contains a variety of specific elements and belongs to an interesting type, known as “double sundial”, as it combines 2 scales: traditional sundial in horizontal plane and a stereographic projection of celestial sphere. Double sundials were described by William Oughtred in 1630s and were popular in England in XVII-XVIII cc. Comparing the readings of both dials their position could be adjusted without a need for a compass. To provide higher precision, the hour scale is drawn in the form of transversal lines, otherwise known as “nonius” scale, and a table of corrections of “equation of time” based on calculations done by John Flamsteed in early 1700s. Also the dial contains a windrose and a lunar dial – a scale to convert the time obtained by the readings of the sundial from the shadow of the gnomon from the moonlight, depending on the day of the lunar cycle. The recreated dial will be installed into the original stone pedestal in the process of restoration of the castle park. The described elements can be used in contemporary sundials designed as teaching aids for learning sciences.