When Silas Hiram arrived at what was called at the time New Earth (later called Helome by the Vuduri), his one luxury item was a telescope.
He spent many years building up his farm and in the evenings, he'd look up at the stars. Because the A and B star of Alpha Centauri are separated only by 80 AU, the second star, called Beth by the residents, was very bright; far brighter than the moon. Because of the alignment, for many, many years, Beth obscured Silas' obsession, Sol and by definition, Earth.
There came a time when Beth set before the main star, called Aleph, and the night sky was finally dark enough that he could see it with his telescope. However, to get the telescope properly aligned, he used what is called the red dot finder to calibrate the telescope. That was how he noticed that Alnilam disappeared which, 14 centuries later, became a really big deal.