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This morning I was able to set up the artificial star, between two downpours, and collimate the secondary.
First I used a 10mm eyepiece and then I plugged in a ZWO ASI120MM, which is a better way because the eye's astigmatism is less involved.
Then I decided to go the extra bit and captured 10sec AVIs on both sides of focus. After stacking, I put the images through the Roddier software to see just how good this scope is.
The conclusion is that it is not great, but not too bad for a mass produced instrument. The main mirror seems to have a bit of a trefoil error, with one of the "lobes", near the edge, having quite a bit of a departure from the required tolerance. Although it is a small area, it increases the peak to valley error to 1/2 wave. The Strehl ratio of 0.77 is a bit short of the diffraction limit but not bad for long exposure imaging where the seeing would dominate anyway.
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