 Molar ratio of carbon monoxide to water in 2I/Borisov tail is 35%-105%, resembling unusual blue-tailed comet C/2016 R2 while average for solar system comets is 4%.As seen from Earth, the comet was in the northern sky from September until mid-November.It crossed the ecliptic plane on 26 October near the star Regulus, and the celestial equator on 13 November 2019, entering the southern sky.