Hope the colour correction is better than that of the WO Megrez 88.
Nearly bought one of these, but was lucky enough to have chance of trying one before making a decision.
Although, in focus, the colour correction was ok visually (red fringing inside or outside of focus), the stars in my SXVF-H9C images, had beautiful red fringes aound them.
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Needless to say, I didn't buy one!!.
I guess it was to be expected from a doublet, employing a fast f/5.6 focal ratio.
I decided to buy the Meade 5000 Triplet APO instead, and that's a 'clean as a whistle'.
Hopefully, as the Megrez 90 is a longer focal with a slower f ratio, you should be ok.
Dave