Sunspot Observations by Barnaba Oriani (1778 – 1779)

Nogales, J.M., Carrasco V.M.S., Arlt R., Domínguez-Castro F Vaquero J.M. (2020). Sunspot Observations by Barnaba Oriani (1778 – 1779). Solar Physics 295(71),1-16 . doi: 10.1007/s11207-020-01638-8

We present the sunspot observations made by Barnaba Oriani in 1778 and 1779 at the Brera Observatory (Milan, Italy). We have computed the number of sunspot groups and individual sunspots and extracted the positions of all individual sunspots recorded by Oriani. It must be highlighted that the observations made by Oriani in 1779 are not included in the current sunspot-group number database. The observations made in 1778 were already included, but we have found important deficiencies in these values that underestimated the true level of solar activity. The highest daily number of groups recorded by Oriani was 12 (24 August 1778). Only Horrebow in Solar Cycle 2 observed a higher daily number of groups (up to 16 groups in 1769) in the second half of the 18th century. We have compared the sunspot observations made by Oriani and Staudacher for the common dates. In general, Oriani observed a few more groups than Staudacher, while Staudacher recorded more individual sunspots than Oriani. Furthermore, the sunspot positions recorded by both observers are similar, but some significant differences can be found. Finally, we want to highlight that the sunspot records made in the 18th century will help us to understand better the behavior of the long-term solar activity. Therefore, we need to improve the observational coverage of the sunspot records carried out in that century.

Impact factor: