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It's reasonably easy to collimate a refractor using a Cheshire eyepiece if the lens cell is adjustable. This looks like one or more of the elements is de-centred with respect to the other two, and is not a simple fix. Check that the shims between the elements are intact and in place (assuming it is an air-spaced objective) and is there any chance one or more of the elements were rotated with respect to the others? Alternately if the aberration doesn't change across the FOV then it may be a matter of a severely bent tube?
Good luck!
Andrew
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