Adapter rings and T adapters

T rings, rings or adapters is that astrophotographic accessory that is placed in the telescope's eyepiece holder and is threaded to the specific T2 adapter or ring for each camera model.

There are simple T adapters directly to the eyepiece holder, M adapters that are threaded to the T2 ring and to the eyepiece for the type of afocal photography and others that incorporate a barlow lens to achieve more magnification in photography.