An optical viewing system includes first, second and third image modifying devices together with an adaptor assembly for connecting the image modifying devices together. The adaptor assembly has first and second clamping portions. The first clamping portion is connected to the first and second image modifying devices and the second clamping portion is connected to the first clamping portion and to the first and third image modifying device so that the first image modifying device is clamped between the second and third image modifying devices. At least one of the first and second clamping portions are removably connected to the first image modifying device so that the first image modifying device can be removed from the adaptor assembly and operate as a further independent optical viewing system. Different combinations of image modifying devices can be arranged with one or more of the clamping portions.