My 12-inch Meade LX200 Classic telescope has been in storage for perhaps 3 or 4 years. I moved to a new town and it has taken me this long to finally build a new observatory for it. It has become apparent that the instrument has developed some sort of optical issue as it is pretty much impossible to bring a star to focus.
I've captured a series of images, starting well out of focus and slowly approaching what should be close to focused. The numbers in the images represent the position of my Optec TCF-S focuser, so 6500 steps is with the focuser almost all the way out, each image moving focus inwards to 3500, the center position, which should be close to focus.
Not pretty, is it? My guess is that it is a farly severe astigmatism, but what could cause this? The scope was OK when it went into storage, so what could have happened in the meantime? Where do I start with diagnosing and remedying this?