SBIG FW8S-STT Standard 8-Position Filter Wheel for STT
Standard 8-Position Filter Wheel for the STT series cameras. This filter wheel does not have the built-in self-guiding CCD. It is compatible with Canon EOS and Nikon lens adapters.
A new filter wheel design for the STT series sets it apart from other designs. The carousel holds eight 36mm filters and inserts are available for 1.25\" filters. Two new unique features make this an imager\'s delight: First, the design incorporates a self-guiding CCD in the filter wheel cover so that light from the guide star is captured before passing through the filters. An optional filter wheel cover is available for wide angle imaging with Nikon or Canon 35mm camera lenses, or for anyone who does not need or want the built-in self-guiding. Full sets of 36mm LRGB and Narrowband filters by Astrodon, Baader Planetarium and Astronomik are available for unvignetted imaging at any f/ratio.
The second unique feature of the STT filter wheel is a positive centering mechanism that precisely re-positions and firmly holds filters in exactly the same position over the CCD every time, regardless of a loss of power or intervening movement of the filter wheel.
In our tests of the new design, using an STT-8300, the re-positioning of the filters was accurate to better than 5.4 microns after several complete rotations of the filter carousel. This degree of precision means that flat fields taken after the filter has moved and returned are accurate to a single pixel. An example of the improvement in flat fields with this kind of precision is demonstrated in the comparison images below.
The image at left, above, is a large opaque spot on a filter in STT filter wheel. The filter carousel was rotated several times before the filter was moved back into the optical path and a flat field was taken. The image at right shows the resulting flat field image.