Go Out:  Look Up!

A Guide to the Sky, Telescopes, and Telescope Programs

Home How a Scope Works Using a Scope Note to Parents Aiming a Scope Using a Finder Eyepieces Using a Zoom Fun Equipment


Installing the Eyepiece

The eyepieces go into the focuser.

Make sure the two thumbscrews are unscrewed enough that the do not protrude into the barrel.

Slide the eyepiece into the barrel.

Tight both screws finger tight. 

For non-zoom eyepieces, you do not need to overtighten the screws.

For zoom lenses that twist, the screws should be fairly tight to prevent the eyepiece from turning when zooming in or out. 

  • If you can't get the screws tight, use one hand to hold the bottom of the eyepiece and the other to zoom in or out.

Installing an Eyepiece Filter

Filters, such as a moon filter, have male threads along their circumference.  Most eyepieces have female threading along their interior bottom.  The filter screws into the bottom of the eyepiece. 

Note: that the threading is very fine.  Do not force the filter.  Generally, if it won't screw in, it maybe misaligned. Unscrew it and try again. 

The filter does not need to be "cranked" all the way down on the Celestron Zoom lens (it's field lens prevents it from screwing all the way down).

Eyepiece and filter separate

Filter screwed onto eyepiece

Note the fine threading Note the gap between the eyepiece and the filter bezel.

Moon Filter

Use a Moon Filter any time you are observing the moon, other than when it is a thin crescent.

Questions or comments? Email:Jeff Martin