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If you are using a laser that you can observe from the primary mirror end, watch the location of the return spot as you swing the OTA from horizon to zenith. Bet you it moves on these mass produced ones. It moves about a mm on my 12" GSO dob. I collimate at around 50-60 deg elevation.
ps. it's worth cranking the focusser all the way in and out and watching that return spot (and the spot location on primary mirror as well). Big movement means issues to be sorted, as Geoff says.
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