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Hi Simon,
If you look at some of my previous posts you will know that almost all of my problems have been caused by collimation problems first with the alignment of the secondary and the focuser.
These Chromatic abberrations you talk of are almost 100% due to slight misalignment of the optics when you took them out to clean them, they didnt line up perfectly when they went back in.
My suggestion is to collimate with cheshire/laser tool as close as you can and then at night on a BRIGHT star or Jupiter, wind the focuser ALL the way out with a low power eyepiece and then adjust very slightly the tilt of the primary mirror until the distance around the secondary shadow is even ALL the way round.
Make sure that when you do the slight alignment adjustments that you keep the star in view. If you get to the edge of view when adjusting, stop then recentre, check and continue, the last thing you want to do when fine tuning is lose the star/planet you are looking at. Periodically return to focus and check if the CA is still there. Once you fine tune it all up, you should (and I mean should) see a dramatic reduction or even elimination of the CA.
If you look closely, when you switch from near to far focus just off actual focus, you may see the flaring move 90 degrees from in to out. This should disappear when you tune it all up.
Hope this helps.
Chris
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