This adapter from Baader Planetarium is what Takahashi refractor owners have long been waiting for. This # T2-12 / 2458199 adapter converts the internal M43x0.75 threads used by Takahashi on the visual backs of all their focusers into external T-2 (M42x0.75) threads.
Its extremely thin 1mm profile results in virtually no loss of backfocus distance. Convenient grip slots make installation or removal a snap. With this adapter, Takahashi owners can now access the full range of Baader Planetarium accessories. Note: This adapter does not fit Vixen (it is not the same M43 thread pitch as the Vixen T2-22).
In particular, Baader highly recommends using the Clicklock Eyepiece Clamp (T2-08 / 2458100) to provide a superior eyepiece holder. Its strong 3-point clamping action prevents all movement of the eyepiece or camera, unlike the standard Takahashi clamps which allow significant movement of the eyepiece as well as mismatch with eyepiece grooves (particularly harmful for imaging or use as guidescopes). Another popular accessory combination for Takahashi telescopes is the Quick Change System. With this system, you can close-couple cameras or use any of the Baader Diagonals (T-2 Prism, Amici or T-2 Maxbright). These diagonals are the ideal high-quality match for the superb optics of Takahashi scopes.
Total adapter length = 10.6mm (0.42")
Optical length = 1mm (0.04")
Length of male T2 thread = 3.5mm (0.14")
Length of male M43 thread = 3.5mm (0.14")
Maximum outside diameter = 45.9mm (1.81")
Weight = 0.4oz.