Many of today 's hobby telescopes are much stronger than his , so anyone can easily follow in his footsteps and cast the same gaze . four of Earth 's four great moons crossed its sunny side in the last 15 years . That 's rare ; it has happened only twice in January . Carol Christian 's images are primarily for aesthetic purposes , a gift to the public .
four of Earth 's four great moons crossed its sunny side in the last 15 years . That 's rare ; it has happened only twice in January . Carol Christian 's images are primarily for aesthetic purposes , a gift to the public .