Page "Aberration of light" Paragraph 23

The instrument was set up in November 1725, and observations on γ Draconis were made on the 3rd, 5th, 11th, and 12 December.

There was apparently no shifting of the star, which was therefore thought to be at its most southerly point.

On December 17, however, Bradley observed that the star was moving southwards, a motion further shown by observations on the 20th.

These results were unexpected and inexplicable by existing theories.

However, an examination of the telescope showed that the observed anomalies were not due to instrumental errors.