I owned a SkyWatcher 127 Mak a while back and did the flashlight procedure of measuring the working aperture by projecting a flashlight thru an eyepiece with the focus at infinity and measuring the corresponding projected disk. The disk is supposed to represent the working aperture of the scope. I read posts here on CN of measurements of 118-120mm or thereabouts leading to the conclusion that the primary may not be the 127 mm as advertised. My results were in that range.
Now I have a new SkyWatcher Skymax 127 mak. Doing the flashlight “test” I got 123 mm. By turning the focus more to the infinity direction, I got 130 mm. I am now having doubts about the validity of this altogether. Maybe the only way to really know what the true working aperture is would be by direct measurement of the primary mirror.
Don’t think many of us will be trying that...FWIW, as a side note, collimation was perfect out of the box, at least with an artificial star.