STUDY OF MAKING A HORIZONTAL SUNDIAL WITH A STRAIGHT ZENITH-DIRECTED GNOMON IN NGAWI REGENCY

• Main Author: Rainyta Saffira, Dhea
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/75407
• Institution: Institut Teknologi Bandung

<p align="justify"> Sundial is a device used to indicate the time according to the Sun’s apparent motions in the sky. Sundial consists of two parts, the first is a style which we refer to as a gnomon, and the second is a plate or table printed with hour lines to mark the hours which we refer to as the table of dial. The gnomon casts a shadow on this table, and its length and direction change accordingly to the Sun’s apparent motions. This cast shadow is what people use to indicate time. This work was done in Ngawi Regency, precisely on 7°24?07?? S, 111°27?48?? E, 166 meters above sea level, using 8 sets of instrument props which each of them consisted of a horizontal board made of Eternit board, a gnomon made from plastic ballpoint tube, and an observation paper sheet which is fixated semi-permanently above the horizontal board. These instruments were placed at a (375.5±0.05) cm height above the land, with zenith-directed gnomons of (9.10±0.05) cm height. Observation paper sheets are used to record the positions of the casted gnomon shadow tips relative to the gnomon’s position, and later after 7-9 times of observations, are scanned to gain the digital image JPEG files that contain pixel information. An astronomy image processing software, IRIS, is used to determine the position of the casted shadow tips recorded on the observation paper sheets by using the informed pixel locations. After these datas are collected, we used Microsoft Excel and Python Programming Language to plot the data, resulting in 77 curves of the recorded casted gnomon shadow tips from May 9th, 2020 until July 25th, 2021. Based on that result, we could determine where the true north is located and this information will be useful as a basis for sundial construction on the observer’s latitude.