I suppose there was a time when Vixen dovetail bars were the gold standard for attaching scopes to mounts. However, when mount manufacturers moved to supporting both Losmandy and Vixen attachment in a single clamping system, things got crazy. Look at most of the mounts that support duel clamping: the newer Skywatcher, Celestron, etc; and they usually solve the problem by recessing the Vixen rail clamp inside the Losmandy clamping system. This leads to problems when mounting scopes that come with Vixen rails, as inevitably something seems to foul against the clamping system jaws or the base. Here is a good example:
The new TS (or SharpStar) 71SDQ, which comes with a Vixen rail, it simply would not fit my CGX mount in a reasonably balanced position. Check out the yellow line in the first photo. Because the focuser tension screw hangs down like dogs balls, the base of the CGX clamp prevents sliding the scope forward. So the 71SDQ would hang off the back of the clamp, totally unbalanced and only clamped on the forward section of the Vixen rail. In addition, the focuser knobs would hit the CGX Losmandy clamp jaws if it was able to slide forward, because there is not enough rise in the Vixen rail to clear the Losmandy jaws. This design might suit something like a HEQ5 or something similar with a short single jaw system, without a recessed position, but it requires modification for use on dual jaw systems.
So here is my solution, which I have used for other scopes as well, and which suits probably any Losmandy clamping system. Photos attached.
I simply install a new Losmandy base plate, using the original Vixen rail as a riser. As the scope is no longer sitting in the recessed Vixen clamp, there are no clearance issues anymore, and the scope can be moved fore and aft to acheive the desired balance.
The obvious solution is to order the scope with a Losmandy plate installed, or at least have a couple on hand if you need them, and let your creativity solve the problem. But should we have to re-engineer the mounting system for each scope we buy?
I had a similar problem. I am mounting Skywatcher Star Adventurer components on my Vixen Polarie portable tracker and the vixen dovetail of the Skywatcher is about 1mm wider than the Swiss Arca dovetail holders. Enough so they won't fit!
I swapped out the vixen dovetail plates a fair few yrs ago for the d series losmondy plates due to the extra surface support when your telescope is horizontal. The vixen plates are still good for the smaller gear but I've changed to the even smaller Arca Swiss for this, which a lot of camera mounts use as well.
(they also have a good range of gear.)
