Reconstructed sunspot positions in the Maunder minimum based on the correspondence of Gottfried Kirch

We present reconstructed sunspot positions based on observations reported in letters between Gottfried Kirch and other contemporary astronomers from AD 1680 to 1709, that is in the last decades of the Maunder minimum. The letters to and from Gottfried Kirch in Latin and German language were compiled and edited by Herbst (). The letters (and observations) from Kirch are mostly by Gottfried Kirch, but some also by his second wife Maria M. Kirch (married 1692) and their son Christfried Kirch (born 1694). Using excerpts from the letters, some with drawings, we found some 35 sunspot groups (often for several days in a row or with interruptions) by Kirch and/or his letter partners (in three cases, only the month is given: 1704 January, February, 1707 March, otherwise always the exact dates)usually one group at a time. We also found 17 explicit spotless days, several of them new (previously without any known observations). We could constrain the heliographic latitude by Bayesian inference for 19 sunspot groupsfive of them completely new (one group 1680 May 20-22 from Kirch and Ihle, one to two groups 1680 June 15-23 for Kirch, one group 1684 May 6 from Ihle, and one group 1688 December 14-15 from Kirch), while the others mostly agree (within 2 sigma) with previously published values for those dates by others. With these data, we then amend the butterfly diagram for the Maunder minimum. By comparison of our data with the sunspot group catalogue in Hoyt & Schatten (), we noticed a number of discrepancies, for examaple, that dates for British observers in the Maunder minimum (Flamsteed, Caswell, Derham, Stannyan, Gray, and Sharp) as listed in Hoyt & Schatten () are their original Julian dates, not converted to the Gregorian calendar (10-11 day offset in Hoyt and Schatten). Most of these modifications also apply to the modified sunspot group catalogue in Vaquero et al. (). We also present two aurorae observed by the Kirchs in 1707 and 1716.