Fluorite Flatfield Converter (FFC) – Barlow.
With the appropriate adapter rings, the FFC enables extreme
Extension factors without affecting the image quality on the
axis or in the field. Where photographic converters or Barlow lenses only
offer a limited extension factor, depending on the optical
Construction 2x, 3x or 5x, the FFC allows a
much wider range with full sharpness performance, namely 3x
up to 8x.
For example, turn your 2″ 30mm wide-angle eyepiece into the
pleasant insight a 4mm planetary eyepiece without sacrificing in
field of vision or in viewing behavior.
The FFC offers a T2 internal thread on the telescope side and one on the camera side
T2 external thread. These photographically very common threads
turn the FFC into a flexible converter that can be connected to all Tele
Fits lenses with a T2 mount.