SBIG FW8S-STXL Standard 8-Position Filter Wheel for 50 mm Round Filters
The FW8S-STXL is indistinguishable from the FW8G-STXL save for the fact that this Standard version does not feature a Self-Guiding CCD incorporated into the front cover. However, the filter mechanism is identical, the wheels have the same base, and the covers are compatible with either model. In fact, to use STXL camera lens adapters for Canon EOS or Nikon lenses with the Self-Guiding model, all you need to do is add a Standard cover.
Micron-Precision Filter Positioning
Like the Self-Guiding version, the Standard STXL filter wheel has the same built-in micron-precision filter positioning mechanism as found in SBIG STT series cameras. Flat field frames must present identical optical characteristics to be most useful. Exact representation of any dust or uneven illumination is crucial for correction by the flat field frame. The STXL filter wheel was developed to provide a high level of accuracy when capturing flats through filters by consistently repositioning the filters to within a few microns. This enables the imager to take flat field frames that are strikingly precise even after performing several wheel rotations or even following power loss.