Sunspot positions from observations by Flaugergues in the Dalton Minimum

Abstract

French astronomer Honoré Flaugergues compiled astronomical observations in a series of hand-written notebooks for 1782$\unicode{x2013}$1830, which are preserved at Paris Observatory. We reviewed these manuscripts and encoded the records that contain sunspot measurements into a numerical table for further analysis. All measurements are timings and we found three types of measurements allowing the reconstruction of heliographic coordinates. In the first case, the Sun and sunspots cross vertical and horizontal wires, in the second case, one vertical and two mirror-symmetric oblique wires, and in the third case, a rhombus-shaped set of wires. Additionally, timings of two solar eclipses also provided a few sunspot coordinates. As a result, we present the time--latitude (butterfly) diagram of the reconstructed sunspot coordinates, which covers the period of the Dalton Minimum and confirms consistency with those of Derfflinger and Prantner. We identify four solar cycles in this diagram and discuss the observed peculiarities as well as the data reliability.

References in corpus (16)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Solar Cycle
• The Maunder minimum (1645--1715) was indeed a Grand minimum: A reassessment of multiple datasets
• Sunspot positions and sizes for 1825-1867 from the observations by Samuel Heinrich Schwabe
• A solar cycle lost in 1793--1800: Early sunspot observations resolve the old mystery
• The butterfly diagram in the 18th century
• Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
• Thaddäus Derfflinger's sunspot observations during 1802-1824: A primary reference to understand the Dalton Minimum
• Solar activity: intrinsic periodicities beyond 11 years
• Strong evidence of low levels of solar activity during the Maunder Minimum
• Christian Horrebow's Sunspot Observations -- II. Construction of a Record of Sunspot Positions
• Sunspot Observations Made by Hallaschka during the Dalton Minimum
• Stephan Prantner's Sunspot Observations during the Dalton Minimum
• Is Cycle 24 the Beginning of a Dalton-Like Minimum?

Cited by in corpus (2)

• Long-lived sunspots in historical records: a case study analysis from 1660 to 1676
• Sunspot Observations in 1684-1702: John Flamsteed and Philippe de La Hire