Aony Alpha 7 cameras are particularly useful for astronomy due to their high sensitivity, short overall length and low weight. This T-Ring, with Sony E-Mount/NEX bayonet, is optimal for the shortest possible adaptation to back focus-sensitive systems such as a Hyperstar or fast Newtonian. It is extremely compact, extending the 18mm back focus of the camera only by an extra 8.3mm. As all the other T-rings of a similar design to T2 on the market cause extreme vignetting, this T-ring is also a suitable possible adapter, along with M48 and T2 and even S52. A 2" sleeve is available for the S52 dovetail ring which can be clamped directly into the S52 ring, thus providing a vignetting-free image field for 2” Sony cameras.

Source:
https://www.astroshop.se/t2-ringar-och-bajonettadapter/baader-kameraadapter-t-ring-foer-sony-e-nex-bajonett-med-d52-m48-och-t2-gaenga/p,49988