Focal Reducer, 0.5X, for Observing and Imaging:
This focal reducer lowers the focal length of the main optics by half, providing a larger field of view. This is advantageous when using cameras with small chips for imaging.
Use:
Using the focal reducer is ingeniously simple. It has a 1.25" filter thread, which fits into any 1.25" eyepiece or 1.25" camera adapter without any problem.
Imaging:
The focal reducer increases the size of the image field and shortens the exposure times when imaging. It is particularly recommended for use with the Philips SPC 900NC Webcam, etc.
Visual observing:
The increase of the size of the field of view with 1.25" eyepieces is particular useful if you like observing more extended celestial objects with long focal length instruments.
The smaller focal reducer/eyepiece distance means that the reduction factor is only 0.5X. However, the focus is only shifted inwards by 5mm.
Technical Data:
Connecting thread: Filter thread 1.25" (M 28.5 x 0.75) on both sides
Free light transmission: Lens aperture 22.5mm
Lenses: 2 lenses for better correction - cemented - coated
Material: Aluminium - black anodized
Reduction factor: approx. 0.5X - depending on distance
Focal length: 85mm
Our expert comment:
The reducer is useful for 0.25 to 0.5 inch chips (webcams, DMK, Watec) and focal ratios from f8 (refractors, Maksutov and SCs). It needs about 5cm of back focus. The result an f4 to f6 optical system. The reducing effect can varied by using the distance from the chip, e.g. by filter rings.
The reducer is unsuitable for DSLRs and large CCD cameras as the chips are not completely illuminated.
(Bernd Gährken)
