Over the next two months, he stayed as a guest, analyzing some of Tycho's observations of Mars; Tycho guarded his data closely, but was impressed by Kepler's theoretical ideas and soon allowed him more access.
I de næste to måneder blev han boende som gæst og analyserede nogle af Brahes observationer af Mars; Brahe bevogtede sine data, men blev imponeret over Keplers teoretiske ideer og tillod ham snart yderligere adgang.