In 1853 he established a private observatory at Redhill in Surrey, where, concurrently with night-time observations for his Catalogue of 3735 Circumpolar Stars (published in 1857), he began a daytime programme of measurements of the heliographic positions of sunspots, which he continued until 1861. The results, published in 1863, included a calculation of the position of the Sun’s axis of rotation to unprecedented accuracy, and measures of sunspot distribution and rotation period as functions of heliographic latitude. He originated the system of Carrington rotations. On 1859 September 1 he made the first observation of a solar flare, which was followed by the greatest geomagnetic storm ever recorded; this is known as the Carrington event.