I have an MK67. I am not sure how the MK66 collimates. I am guessing you have 3 screws on the secondary, but I am not sure about the primary. My primary is fixed, no adjustment necessary or possible.
I will assume your scope is reasonably collimated. Focus with your highest power EP (barlow if needed) on Polaris (or an equivalent magnititude star if your mount tracks) to 400X to 600x. Focus the star to its smallest point. If seeing is OK you should be able to discern the first difraction ring around the star. I adjust -teeny adjustments - less than 1/16 turns, until the star is centered. You are not star testing. You only need glimpses of steadiness. If seeing isn't real bad, you should be able to judge the star relative to the first ring. Hope this helps.
Gregg
I will assume your scope is reasonably collimated. Focus with your highest power EP (barlow if needed) on Polaris (or an equivalent magnititude star if your mount tracks) to 400X to 600x. Focus the star to its smallest point. If seeing is OK you should be able to discern the first difraction ring around the star. I adjust -teeny adjustments - less than 1/16 turns, until the star is centered. You are not star testing. You only need glimpses of steadiness. If seeing isn't real bad, you should be able to judge the star relative to the first ring. Hope this helps.
Gregg
