SBIG FW8G-STT is a self-guiding 8-position filter wheel for the STT Series cameras. This wheel has a guiding CCD and associated optics built into the front cover, in front of the filters. Due to the backfocus requirements, camera lens adapters will not work with this cover. A lower profile standard cover, without guider, is available as an accessory. The standard cover is easily swapped for the self-guiding cover when imaging through a camera lens is desired.
The carousel holds eight 36mm filters and inserts are available for 1.25″ filters. Full sets of 36mm filters for unvignetted imaging at any f/ratio.
The 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, 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 below shows a a large opaque spot on a filter in STT filter wheel (left). 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-fielded image.