English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Digital images of the observations printed in the books "Rosa Ursina sivesolis" and "Prodromus pro sole mobili" by Christoph Scheiner as well as thedrawings from Scheiner's letters to Marcus Welser are analysed in order toobtain information on positions and sizes of sunspots that appeared before theMaunder minimum. In most cases, the given orientation of the ecliptic is usedto set up the heliographic coordinate system for the drawings. Positions andsizes are measured manually on the screen. Very early drawings have noindication of their orientation. A rotational matching using common spots ofadjacent days is used in some cases, while in other cases, the assumption ofimages being aligned with a zenith-horizon coordinate system appeared to be themost probable. In total, 8167 sunspots were measured. A distribution of sunspotlatitudes versus time (butterfly diagram) is obtained for Scheiner'sobservations. The observations of 1611 are very inaccurate, the drawings of1612 have at least an indication of their orientation, while the remaining partof the spot positions from 1618-1631 have good to very good accuracy. We alsocomputed 697 tilt angles of apparently bipolar sunspot groups observed in theperiod 1618-1631. We find that the average tilt angle of nearly 4 degrees isnot significantly different from 20th-century values.

Sunspot positions, areas, and group tilt angles for 1611-1631 from observations by Christoph Scheiner