[raymo]

Hi Tony, Cone error is when the scope is not perpendicular to the RA axis of
the mount[parallel to the saddle that the dovetail bar fits into.
Scopes normally come with adjusting screws on their dovetail rails.
You don't have that luxury, so you could use very thin metal shims on the bottom of your dovetail bar, and once correct alignment is achieved glue them in place on the bar. Just insert a shim between the bottom of the dovetail and
the saddle at one end or the other, and tighten the dovetail.See if it makes things better or worse.
If it improves things add more shims until error is eliminated, and obviously
if it makes things worse, shim at the other end instead.

To check error before you begin adjustments you ideally need a reticle or crosshair eyepiece, or an eyepiece you don't care about much which you can mark in
the centre with a fine marker pen.
Take rig outside and find a small target at least a few hundred metres away.The lamp unit on top of a street light would do.
Rotate mount so that counterweight shaft is parallel to the ground.
aim the scope to centre the target on the cross hairs and lock the scope.
Rotate the mount so that the CW shaft is parallel to the ground on the opposite side of the mount, and see if the target is still centred in the eyepiece.
raymo