Hi Tim the Takahashi sky90 is a great scope , performs way better than a 90mm f5.5 should .
On the mounting of a Tak to Vixen just buy a short dovetail from Andrews or Bintel and bolt it on to the Tak clamshell as I have done here , its my sky90 on Viven SP mount , this is an awesome set up .
I will try and find a photo of my now sold FS60C on a GSO alt/az mount and post it for you
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Brian.