This ring system has an inside diameter of about 125 mm. This is the perfect size for holding our new SVX090T and our 102mm refractors atop a larger telescope.
When mounting a guidescope on top of another telescope, it is necessary to use adjustable rings. Adjustable rings allow the top telescope to be moved slightly in relation to the main telescope. This is necessary because if non-adjustable hinged rings are used, the two instruments will never be pointed in precisely the same direction. When using the top telescope as a guidescope, super finder, or alternate wide field telescope, adjustable rings will allow the user to make sure each telescope is centered on the same object. When doing astrophotography, adjustable rings will make it possible to use the top telescope as a guidescope, pointing it at a guide star while the main telescope is centered on the object being photographed.