The preferred method of attaching a Short-Tube or
Wide-Field refractor to the LX90 OTA is with a
Losmandy bracket
and dovetail system. But this costs hundreds of AU$. So, why buy when
you can build your own bracket for a fraction of the cost?
I own a Sky-Watcher 804 achromatic refractor and the AZ3
mount. You can check out the specifications of this little scope by
following the Equipment link. It took me a
while to hunt down one of these in the Meade royal blue colour. My
intention for purchasing this little scope was two-fold: I wanted a
travel scope that I could take with me for quick views of the night sky,
and secondly I had plans to mount it on top of my LX90 to use both as a
guide scope and for capturing wide-field images of the night sky.
This image shows the method of attachment of the bracket
to the LX90 OTA. The PVC tubing screws to the OTA using the two existing
bolts. The timber wedge (Tasmanian Oak - hardwood) is attached to the PVC
by two countersunk screws (see below), hard rubber spacers, then the
timber horizontal stay (Tasmanian Oak) by two hex bolts at each end.
Collimation in altitude (or DEC) can be adjusted via the hex bolts at
both the front and rear of the stay (eg. tightening those at the front
to the scope will cause the ST80 to dip)
Side-on view of bracket end showing the method of
affixing the PVC tubing to the timber wedge by two countersunk
bevel-head screws.
This top-down view shoes threaded metal collars that the
hex bolts screw into. These collars are themselves screwed into the
timber from the bottom up and it is impossible for them to be pulled out
by over-tightening the hex bolts.
Underside of PVC section attached to the timber. the
central hole allows this bracket to fit over the top of the centre bolt
on the OTA (which remains in position).
Close-up view of bracket with ST80 attached. The quick
release mounting rings that came with the AZ3 mount attach to a slider
mechanism (see below). In this image, you can also see the routered arcs
that allow for collimation in azimuth (or RA). The radius of the arcs is
equal to the distance between the attachment bolts for each of the
rings. I have the rings set as widely apart as possible to aid
stability.
Wider view of the above image showing perspective
Top view (ST80 removed) showing routered arcs to permit
azimuth collimation. the rings are attached to the slider mechanism (see
below) by two hex bolts.
This image shows the underside of the bracket stay
revealing the slider mechanism. Metal collars allow the hex bolts,
affixing the rings, to be screwed into the slider plate. The image also
shows the self adhesive rubber spacers at each end of the stay.
