Sunspot positions and sizes for 1825-1867 from the observations by Samuel Heinrich Schwabe

TL;DR

This study digitized and analyzed over 8,400 historical solar drawings by Schwabe, extracting about 135,000 sunspot measurements to create a detailed, accurate database of sunspot positions and sizes from 1825 to 1867.

Contribution

The paper introduces a comprehensive, digitized database of historical sunspot data with inferred orientations and precise measurements, enhancing solar activity records from the 19th century.

Findings

Approximately 135,000 sunspot measurements collected.

Sunspot positions accurate to about 3 degrees heliographic.

A Bayesian method inferred orientations of drawings without explicit indicators.

Abstract

Samuel Heinrich Schwabe made 8486 drawings of the solar disk with sunspots in the period from November 5, 1825 to December 29, 1867. We have measured sunspot sizes and heliographic positions on digitized images of these drawings. A total of about 135,000 measurements of individual sunspots are available in a data base. Positions are accurate to about 5% of the solar radius or to about three degrees in heliographic coordinates in the solar disk center. Sizes were given in 12 classes as estimated visually with circular cursor shapes on the screen. Most of the drawings show a coordinate grid aligned with the celestial coordinate system. A subset of 1168 drawings have no indication of their orientation. We have used a Bayesian estimator to infer the orientations of the drawings as well as the average heliographic spot positions from a chain of drawings of several days, using the rotation profile of the present Sun. The data base also includes all information available from Schwabe on spotless days.