Karl von Lindener’s sunspot observations during 1800–1827: Another long-term dataset for the Dalton Minimum

Abstract

On a centennial timescale, solar activity oscillates quasi-periodically and also tends to occasionally get into a low-activity period. The Dalton Minimum (circa 1790s–1820s) was one of such low-activity periods that had been captured in telescopic sunspot observations. However, it has been challenging to analyse the Dalton Minimum, as contemporary source records remained mostly unpublished and almost inaccessible to the scientific community. Recent studies have established reliable datasets for sunspot group number, sunspot number, and sunspot positions. This study further analyzes independent Silesian sunspot observations from 1800 to 1827 in a manuscript from the Library of Wrocław University (Ms AKC.1985/15) and complements it with the metadata for the observer: Karl Christian Reinhold von Lindener. We identified 547 days of sunspot observations in these records and derived the sunspot group number, individual sunspot number, and sunspot positions between 1800 and 1827. The results of this study have significantly revised von Lindener’s sunspot group number, which was previously known for only 517 days in scientific databases, and removed contamination from general descriptions. Using our results, we extended investigations into individual sunspot counts and derived their positions. In our analysis, we locate von Lindener’s sunspot positions in both solar hemispheres and contrast the Dalton Minimum with the Maunder Minimum, adding further independent credits to the previous results for Derfflinger’s and Prantner’s datasets. Sunspot positions are also slightly biased towards the northern solar hemisphere in early Solar Cycle 6 (1812–1813). The high-latitude sunspot positions indicate the onset of Solar Cycle 7 as early as June 1822.