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Knife-Edge Focuser Interface Description

Knife-Edge Focusing Procedure [PDF]

Knife-Edge Focuser Calibration Procedure [PDF]

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Astro Camera FAQ

Mitsuboshi Knife-edge Focusers
for Film and Digital SLR Cameras

Mitsuboshi knife-edge focusers are available for film and digital SLR cameras. The focuser works by temporarily replacing the camera back at the camera's lens interface. Refer to the Knife-Edge to Scope Interface description page for details on how the focuser is attached to your scope.

Each focuser includes a circular knife-edge with a clean 10 micron thick metal-on-glass edge which is centered in the field of view. Slewing the target star in any direction will conveniently encounter the knife edge, and it is particularly convenient for semi-helical focusers (helical focusers in which the eyepiece holder rotates).


Each focuser is sold as a set (part number AD-KF35) consisting of the knife-edge holder, locking ring, and a Kenko C-mount adapter specific to your camera.

Pentax 67 focuser sets (AD-KF67) consist of a focuser set for a Pentax 35mm camera, plus an additional Pentax adapter to convert from a 35mm Pentax bayonet to the Pentax 67 bayonet.

Knife-edge holders and locking rings are also available separately.

At the time of purchase, customers have the following calibration options:
  • Send your camera to Hutech for precision calibration to your camera.
  • Send your camera flange-to-pressure plate measurements to Hutech for precision calibration.
  • Have Hutech set the focuser to the nominal camera flange-to-pressure plate distance.
  • Perform the calibration yourself (see Mitsuboshi Knife-edge Focuser Calibration procedure).

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