A few years back I tried a 5x Powermate with a Lunt LS60-THa scope. Last summer I tried a 3x Explore Scientific extender with an RC6 scope. I was using a CCD camera with the Lunt and a DSLR with the RC6. In both cases I saw wavy lines. A few months ago I saw a comment in a CN thread that the problem was caused by .... I can't remember.
I am considering buying a 2.5x PM or 2x ES for lunar imaging with a 100ED and RC6. I've had success in the past with a 2" 2X PM and my Lunt LS60Tha but worry that it might be a problem with the 100ED and RC6.
My goal is close-ups of the moon with optics that can be handled by my iOptron CEM25 mount. Close-up is a relative term when my main OTA has to be under 12lbs.