The State Archives of Belgium, in particular, the archives of Archduke Albert VII of Austria, hold a letter which possibly is a copy of the letter, or an excerpt of the letter, of Kepler to Emperor Rudolf II of October 1604 on SN1604, that is, the first letter of Kepler on the subject. Together with this letter, there are other letters on SN1604, written by Johannes Brengger and Michiel Coignet. In one of these letters, the very observation by Brengger which Kepler cites can be found. The letters are in Albert’s archive because he asked his Court Mathematician Coignet about the phenomenon. It is less clear why Albert was interested in the phenomenon, given the lack of interest in science at his court.

中文翻译：

---

天文学与大公：奥地利阿尔伯特七世档案中布伦格、科涅和开普勒关于 SN1604 的未公开信件

比利时国家档案馆，特别是奥地利大公阿尔伯特七世的档案馆，保存着一封信，其中可能是开普勒在 SN1604 上写给 1604 年 10 月鲁道夫二世皇帝的信的副本或信件的摘录，是，开普勒关于这个主题的第一个字母。与这封信一起，SN1604 上还有其他信件，由约翰​​内斯·布雷格 (Johannes Brengger) 和米歇尔·科涅 (Michiel Coignet) 撰写。在其中一封信中，可以找到开普勒引用的布伦格的观察。这些信件在阿尔伯特的档案中，因为他向他的宫廷数学家 Coignet 询问了这一现象。鉴于他的宫廷对科学缺乏兴趣，不太清楚为什么阿尔伯特对这种现象感兴趣。