I “accidentally” took apart my Celestron 20 mm erect image eyepiece. How do I put it back together?

Care must be taken to keep the disassembled pieces clean and lenses unscratched while reassembling the eyepiece. Prepare a clean surface on a desk or table for the reassembly.

The disassembled eyepiece will consist of six parts. Top, up or uppermost will mean the eye end of the eyepiece. In the order of assembly from bottom to top, these are the pieces.

The largest part is the main body (barrel) of the eyepiece itself.  The name of the eyepiece is on the top of the eyepiece barrel.  

The second piece is a spacer. It is round and stepped and about .75 inches high. The narrow end will eventually go down into the eyepiece barrel.

The third piece is a lens. It is the bigger of the two lenses of the disassembled eyepiece. (If you look closely you'll see that it's actually two pieces of glass cemented together.)  One side is flat, and one side is curved.

Take the stepped spacer and place it on the table (narrow end down). Place the big lens with the curved side up into the larger diameter end of the spacer.

Next, place the spacer and lens into the eyepiece barrel. The narrow step end of the spacer will go down into the eyepiece barrel. Be sure that the lens is correctly in place on the spacer and not tilting at an angle after you drop it into the eyepiece barrel. Double check that the curved surface of the lens is uppermost.

The fourth piece is another spacer.  It is not stepped on the outside. On the inside, one end is stepped, and one end is beveled. Put the spacer down on the table so the beveled end is upright.

The fifth piece is the second, smaller lens. It also has a curved and a flat surface. Place this lens on top of the spacer (part four) so that the flat surface is uppermost.

Now take the smaller lens and spacer together and place them over the larger lens already in the eyepiece barrel. The inside step on the smaller spacer will fit over the larger lens. Be sure it is seated on this lens.

The sixth and final piece for reassembly is the eyecup. 

Gently place the eyecup threads on to the eyepiece barrel and screw the eyecup on the barrel. Be careful not to shift any of the previously assembled parts out of position, as you reattach the eyecup. Avoid cross-threading the two pieces.

Tighten the eyecup with moderate but not excessive turning force.

Note: disassembling an eyepiece may void its Celestron warranty.

Updated 12/18/13