Ash-Shaykh Bin Baaz rahimahullah on the ruling of modern devices such as telescopes to sight the crescent:

“…The apparent legal evidences do not oblige people to observe the crescent using modern devices. It is enough to see the crescent with the naked-eye. However, if a Muslim of upright character uses any of these modern devices in sighting the crescent after sunset, this is unobjectionable because these modern devices depend on the eye and not on astronomical calculations.”

[Reference]

Mentioned by

Bashir
Abu Nu’man