What star is sometimes used as a reference point for spacecraft altitude control due to its angular distance from the Sun and the juxtaposition of its brightness with surrounding astronomical objects?

Commonly known as Alpha Carinae, Canopus is the second brightest star in the night sky with a visual magnitude of 0.73. In 135 century BC, a Syrian Stoic philosopher named Posidonius estimated the size of Earth based on observations of Canopus near the horizon.

Asked by Vasilii Kulev · Last updated 4 years ago · 1.4K views · SOURCE