TheSkySearchers

I bought a used 120ed and the optical performance was deplorable. Here is how I fixed it. Tools needed- spanner wrench with needle point ends to go into the tiny drilled holes of the lens retainer ring. My ring was tightened so much had to use a strap wrench to hold lens cell while loosening ring. The 3" PVC fitting is used to hold lens up while dropping lens cell down. There is a thin paper gasket between the lenses. Lenses have 2 pencil lines on glass that were lined up.

I rotated the top lens clockwise 90 degrees, then reassembled everything and went out to look at Jupiter. The view was better.

The next day rotated the top lens another 90 degrees clockwise and the view that nite was even better.

The 3rd day rotated the lens only 45 degrees and the view was not better.

The 4the day rotated the lens 3/16 of a turn counterclockwise and the Jupiter view was much better.

The last day rotated the lens counterclockwise about 22 degrees for a total of 135 degrees from original placement and this produced the best views of all so far. Marked the lens with arrows pointed toward the sky along a line.

Final Jupiter performance is better than that old 5" Meade f/9 edapo double and not quite as good as the early 5" Explore Scientific triple with the FCD1 glass.

My T.S. Optics 115mm-51 triple, recently built, beats all these 3 quite easily on Jupiter.

CAUTIONS
Put the tube assembly on your mount pointing straight up when attempting to screw or unscrew dew shield or lens assembly. These large diameter threads are very easy to cross thread. If you feel any resistance while attempting to thread on, STOP, and carefully unscrew part. You may feel or hear a click while unscrewing. These are the thread ends passing over each other and they may now be lined up. Start clockwise rotation to screw on, again being very careful. Parts just need to be snug.

My next trick will be stacking spacer rings to see if more lense separation will improve things.

Well done! Having no optical bench this costs several clear nights indeed. Jupiter is quite critical on low contrast details and a good subject for this.
I did something like this on an old achromat which was taken apart by the owner for cleaning purposes. There were no original optical markings.
A small part of one of the spacers was lost during his cleaning action; the lens showed quite a lot of coma too.

Of course his is not recommend for home and amateur-reparation of triplets. There are optical experts who make a living of it. Triplets are not really the cup of tea for us amateurs.