Can I just step in here with a suggestion hattrick? Might I suggest that you do not under any circumstances strip these telescopes any further. And never, ever, never touch the lenses with anything more than a fine camera lens blower type brush or acid free kitchen tissue (usually the cheapest type) rolled onto an ear bud dipped in clean methylated spirit. I appreciate that the real experts will tell you how simple they are internally. But just be warned, there is no such thing as spare parts and a single lens will have to be mathematically formulated/calculated and ground and will cost a kings ransom. Alas, they only come as matched pairs