Ok, good start. So when you are collimating on a star or an artificial star (this can be made out of a simple light circuit and Al foil). Your main focus is the diffraction pattern around the secondary not the secondary itself. Use an eyepiece which give you a resonable high mag, start about 300x. The point of focus is just in or out of best focus (1/4 turn or less) and what you are looking for is how concentric the diffraction pattern is in regards to the secondary. Make sure the diffraction pattern is in the centre of the FOV. Now as the only collimation adjustment a SCT has is on the secondary, choose one give it a tweak CW/CCW, your choice. Re-centre the star look at the diffraction pattern again and if it looks more central your heading in the right direction, if it’s worst, tweak in the opposite direction, re-centre and repeat above process until you are satisfied that the diffraction pattern is concentric around the secondary.
Should note, a cheap way of creating an artificial star is to use a marble, the sun reflecting off it will give you a nice artificial star to work with, is mentioned in the LX200 manual, well the old ones I have seen.
Also if you can do the collimation during the day it will be easier no worries about tracking etc set up the telescope on you mount power up centre the artificial star and star the collimation process. For me usually in the garage looking across the road at my neighbours mail box. Doesn’t work with my LX200 12” due to the near focus being fur then that is I will be using a star.
The only big problem with the Meade 12” is it near focus, which is roughly 40, 50m. So if you can get a clear line of sight for at least 50m plus you should get focus an spend the day adjusting until you get a very nice tie concentric diffraction pattern to the point of a Google Airy Disk.
Other thing to be careful of is don’t loosen the collimation screws to much, I have heard painful stories of secondary falling on to the mirror. If you feel one screw getting to tight, back all of a full turn equally this will not effect the collimation to much. Link below for help on making an artificial star.
https://www.cloudynights.com/topic/4...tificial-star/
Also a good read if you want to dive into star testing.
https://shopatsky.com/products/star-...es-2nd-edition
Anyway keep working on it and again I feel you pain.
Good luck
P.S. kindly help from Zurich at the moment.