The SX DX accessory plate from Vixen Japan is a highly rigid, breadboard style accessories adaptor that will fit directly to any Vixen 45mm style dovetail mounting receptor such as Great Polaris, SXP plus external brands like Synta (Sky-Watcher) and their HEQ5 and EQ6 range of mount as well as Celestron and others. It can be used to mount a host of different adaptors including piggybacking a DSLR or hosting several telescopes at once both for visual or astrophotography purposes.

Above: A typical side by side system on a HEQ5 Pro equatorial mount using the Vixen #2576 SX DX accessories mounting plate with guide scope mounted on the Vixen XY guide mount. Seen here is the classic Vixen AX103S optical tube and a ProStar 80mm refractor used as the guide scope.
Now we all know that basic auto-guide scope can be as simple as a cheapy finderscope arrangement however in many parts of the sky, available stars of significant brightness can be hard to find (the like of say the star field around M83 and others). But aperture and focal length are important for a.) allowing your guide camera to detect and track a faint star in the field and b.) being able to detect subtle drift from periodic error at a single pixel level to ensure corrections to the mount are made effectively and timely. So in a serious set-up, discerning astro-photographers will use at least an 80mm scope for best guided astro-photography results.

Guide scope tube mounting rings with adjustable 3 pivot points on each tube ring is a common set-up. However as the angle of the telescope changes throughout the night, sifting of weight can lead to minor or even major flexure issues resulting in a poorly tracked object (elongated stars). To remove this 3 point shifting risk of slippage, using the solid clamping tube rings that come with the telescope is often preferred and thus.. enter the Vixen X- Y guide mount.

The Vixen X - Y Guide mount

Figure 2

A close up view of this set up shows how adjustments to the guide scope can be made using the fine adjustment knobs that also double as position locking bolts. Not labelled in the centre of the X-Y guide mount is are two release clamps that allow for course adjustment and locking just like the RA and declination clamps found on an equatorial mount. These are generally used only at set up time to set the guide scope "on axis" to the main scope that will be used for imaging.

What I really like about the X - Y guide mount used with the accessory mounting plate is that there are indeed four possible positions along the plate to take the X - Y guider so that centre of weight can be balanced as close as possible over the fulcrum point of your equatorial mount. Thus, if the primary (imaging) optical tube is say a 8 inch OTA (quite fat) then the guide scope can be spaced away from it leaving room for you to get your hand access to the fine tuning X - Y azimuth knobs. But if using two refractors as shown in figure 1  then the scopes can be set close to one another for best centre of balance which is important to lessening strain on motors when slewing to other parts of the sky.

In practice, I found the fine adjust knobs of the X - Y guide mount an absolute pleasure to use after battling for many years with adjusting front and rear 3 prong guide tube rings. The fine adjustment movement of the Vixen X -Y was silky smooth and with 6 degrees or so of adjustment on both axis, finding a suitable nearby guide star quickly was a breeze... no horrible shifting as in the old way!

Above: The primary imaging telescope can be mounted to the Vixen accessory mounting plate using either a Vixen dovetail mounting block or a square style ProStar dovetail receiver. The fitting holes match the Vixen mounting plate identically.

Figure 4
 

Above: From the underside of the Vixen accessory mounting plate, we see the incredible strengthening rib design which is so important for minimising flexure in an optical mounted system intended for serious long exposure astro-photography. Note at the ends of the 16cm dovetail plate the safety bolt heads to avoid the whole thing slipping out of the dovetail mount head when loosening to make balance adjustments. Vixen have thought it all out and it is excellent. The whole guide mount system can be bought here.

I would highly recommend the Vixen accessory mounting plate fitted with their new light-weight though sturdy X- Y guide platform for anyone seeking to minimise flexure in their astro-photography set up. Lessen the frustration and enjoy more productive time under the stars. - SM

See Plate specs here

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