Instructions
Set up the telescopic lens at night when the star is clear of any clouds or precipitation. A clear night will allow you to better focus on an object to test how clearly you can view it through your telescope.
Aim your telescope in the direction of the moon. On bright nights, the moon is an object that you can use to test the abilities of your telescope. Look though the telescope and change the settings to gain a clear view of the moon. You should be able to obtain a clear view without any visual faults, such as blurring. If you cannot clearly view the moon, you will want to have the telescope checked by professionals.
Point the telescope in the direction of a bright star in the night sky. Manipulate the available settings to gain a clear view of the star. If you are unable to clearly view the star, you will want to take the telescope back to the retailer for additional checks.
Focus on other distant objects and manipulate the settings on your telescope to obtain a clear view.