Which preposition to use with eyepieces

of Occurrences 3%

It is said that he watched the operations in comfort while seated before the eyepiece of a periscope carried up through the roof.

with Occurrences 1%

It should have a good prism eyepiece with an angle tube attached so it would not be necessary to break one's neck in reading high altitudes.

of Occurrences 1%

May 21 Eyepieces of Telescopes.

Which preposition to use with  eyepieces