GSO eyepiece adapter # FF021. This is the low / zero-profile eyepiece adapter that GSO includes with all its 2" diagonals and 2" 2x barlow.
This item allows 1.25" eyepieces and accessories to be used in 2" focusers, diagonals and barlows that feature a side notch that allows use of such low profile adapters.The thumbscrew on this adapter is on its side (see photos), so you will not be able to use this adapter completely inside a standard 2" holder without a side notch as the thumbscrew will get in the way of complete insertion.
This eyepiece holder has zero optical length if the upper body of the inserted eyepiece or accessory is not wider than 46mm at its shoulder. For wider items, the optical length will be 4mm.
The eyepiece adapter includes a brass compression ring that restrains the eyepiece and prevents marring of the eyepiece barrel by the metal set-screw. It is precision machined from aluminum and anodized black. It is also threaded to accept standard 48mm filters so you can use your 1.25" eyepieces with your 2" filters (be careful not to let the eyepiece barrel hit the filter though).
- Total height = 1.10" (28mm)
- Optical length = 0mm or 4mm depending on width at sholder of inserted item
- Length of 2" barrel = 0.94" (24mm)
- Thumbscrew specification = M4x0.7 thread with 13mm thread length
- Weight = 2.9oz