Can we draw the following hypothesis from the context? 

Context:

How to use adjustable objective rifle scopes<br>Be sure that your scope is mounted properly. Sighting-in can have been done preliminarily, but additional sighting-in will be desirable after following these steps : Know your rifle. There are actually two optical systems in a rifle scope.

Hypothesis: A scope needs to have lens covers while moving. 
It's impossible to say