Two early sunspots observers: Teodoro de Almeida and Jose Antonio Alzate

Abstract

We present the sunspot ideas and observations of the 18th century Portuguese scholar Teodoro de Almeida (1722-1804) and Mexican scientist Jose Antonio Alzate (1737-1799). We describe the implications of dating a single sunspot observation performed by Almeida in the early 1760s, during the maximum of cycle number 1. A possible solar cycle peak in 1760 (instead of 1761) is investigated. We present several observations of sunspots obtained by Alzate during 1769 (partially associated with the Venus and Mercury transits) and also on 20 July 1786. We estimate 100 +/- 34 as the Group Sunspot Number for this date. These records were unknown and, therefore, not included in the database compiled by Hoyt and Schatten (1998).