Solar rotation elements $i, \Omega$ and period determined using sunspot observations by Ru{\dj}er Bo\v{s}kovi\'c in 1777

TL;DR

This paper revisits Ruder Boskovic's 1777 sunspot observations, describing his original methods for calculating solar rotation elements and comparing his results with modern recalculations.

Contribution

It provides a detailed analysis of Boskovic's original methods and offers a comparison between his historical results and contemporary calculations.

Findings

Boskovic's original numerical procedures are described in detail.

Recalculated values are compared with Boskovic's original results.

The study highlights the accuracy and limitations of 18th-century solar rotation measurements.

Abstract

Ru{\dj}er Bo\v{s}kovi\'c developed methods for determination of solar rotation elements: the solar equator inclination i, the longitude of the node {\Omega} and the period of solar rotation. In his last work Opera pertinentia ad opticam et astronomiam, published in 1785, in the chapter Opuscule II he described his methods, the formulae with figure descriptions and an example for calculation of the solar rotation elements with detailed numerical explanation using his own observations performed in September 1777. The original numerical procedure was performed using logarithmic formulae. In present work we give a description of the original results of R. Bo\v{s}kovi\'c and compare them with our recalculated values.