Orion - SkyWatcher Mount Extension Modification

Introduction

Mount extensions are a great idea for visual astronomy and astrophotography.  They raise the height of refractor telescopes which can be quite helpful when viewing objects directly overhead so you .  For astrophotography they can avoid severe damage as they prevent cameras from hitting the tripod legs while imaging.  This actually happened to me when my DSLR caught the leg during an imaging session, fortunately no permanent damage was done to the camera or mount.  Most mounts can continue to guide well past the meridian if let them as was my case but under certain orientations the camera can hit a leg before reaching the meridian.  Extensions raise the mount head so the telescope has much more room to move freely.

So what do these Orion and Sky-Watcher mount extensions look like and what are their specifications?

Figure 1 and Figure 2 are the ones I am discussing have an outer diameter of 4 inches (10.2 cm) and an inner diameter 3.7 inches (9.40 cm).  Figure 3 shows a new design which is used for the Sirius Pro Mount.  I am only showing this extension as an FYI!

Figure 1 - Orion SkyView Pro Extension
This extension can be used with the Orion SkyView, Sirius, Atlas, Atlas Pro, older HEQ5 and EQ6 mounts.
- $99.00 and provides a 16 inch (36.6 cm) rise.

Figure 2 - Orion Atlas Extension / Sky-Watcher Extension
This extension can also be used with the Orion SkyView, Sirius, Atlas, Atlas Pro, older HEQ5 and EQ6 mounts.
- $99.00 (Orion)/$80.00 (Sky-Watcher) and provides a 8.4 inch (23.3 cm) rise.

 

Figure 3 - Orion Sirius Pro Extension (New Design)
As far as I know this extension can only be used with the Orion Sirius Pro
- $99.00 and provides a 6.3 inch (16 cm) rise.

Problem

The problem with using the extensions is when that there is no way to adjust the mount head once it is attached (Figure 4).  You have to attach the mount to an adapter with a compression screw and tighten it but not too tight and then attach it to the extension (Figure 5).  If you tighten to much, the azimuth screws won't move, too loose and it wobbles.  On more than one occasion I had everything all set, polar aligned the scope, did a star alignment, and then discovered that the screw came loose.  The only way to fix it is take everything apart including removing three tiny adapter plate screws.  

Figure 4 - Mount, Extension, and Tripod

 

Figure 5 - Extension and Adapter

Modification
The fix to this problem was relatively simple after I saw examples from other brands as well as a Sky-Watcher image of telescope rig (Figure 6) with an extension that I cannot find for sale anywhere.  Figure 6 shows an image with an extension that has two access holes so you can adjust the adapter plate screw if it needs adjusting after everything is set up. 

Figure 6 - Sky-Watcher Setup with the Extension (could not find for sale!)

I took my Orion Atlas Extension and using a drill and jig saw with a metal blade, cut out two holes into the extension.  Figure 7 and Figure 8 show the extension with the holes.  I tried to match the size and spacing to what the picture shows. The first hole was larger and oval shaped similar to what was shown in Figure 6 while the second hole was more rounded.  Both of these holes were on one side of the mount as that was how the machined Sky-Watcher Extension was produced. 

Figure 7 - Extension after the holes are cut out

 

Figure 8 - Extension after a fresh coat of paint

I did not need to put in a larger hole because I was able to loosen and tighten the screw with what was done so far.  Figure 9 shows the the extension connected and doing its job.  I am happy with the outcome though it does not look as good as the Sky-Watcher Extension.  Of course I will have to keep an eye on the extension to ensure there is no bending or buckling.

Figure 9 - Extension Complete

 

Of course if it does fail I will report it.