Eye glass
Ocular
Ocular lens is a type of eyepiece that is attached to a variety of optical devices such as telescopes and microscopes.
kids
sera
Yeti
Ally
john Another answer: While "John" is a name, there is no word that ends in "hn" with only four letters.
Another four letter name is Erne.
Connect four.
The astronomer looked through the telescope's eyepiece to observe the stars.
Terminus, finish, deadline, termination.they are the top four i could think off.
Contacting is another name for the word calling.