Focal length reduction and image field flattening (reducer/field flattener) for Schmidt-Cassegrain telescopes
SC telescopes are among the most popular telescopes because they are compact and inexpensive due to their large-scale production. However, the SC optics are not optimised for photography: the focal length is relatively long and the image field is curved. This makes astrophotography difficult. The usable field of view is small and blurred at the edges (exception: EdgeHD from Celestron and ACF from Meade).
The field flattener and focal reducer from Antares
- increases the light intensity: the aperture ratio of f/10 typical for SC telescopes is reduced to f/6.3. This means that the required exposure time is reduced by approximately 40%!
- reduces the focal length and thus increases the field of view. A focal length of 2000 millimetres, for example, is reduced to 1260 millimetres.
- Flattens the image field: Greater sharpness at the edge of the image!
The perfect distance from the camera chip to the front of this optical component is 85 mm. This distance is always calculated from the screwed-in reducer, i.e. without taking the height of the thread into account.
The image field flattener and reducer is placed between the telescope and the camera. For SC telescopes, an SC thread is therefore cut into the housing. Instead, a 2" plug-in sleeve can also be used (see "Recommended accessories"). On the camera side, this reducer also has an SC thread (male) to which further accessories for SC telescopes or an SC/T adaptor for the camera can be attached.
