Simply remove the rear push-fit adapter from the Starwave 2.5" focuser, and screw the flattener into the focuser-end cap for a rigid fit.
The camera-facing rear thread on the Planostar unit is M48 male, which allows the use of the Starwave DSLR Adapter for Canon/Nikon and various Altair Astro M48 spacers for use with CCD cameras.
Use of a large optic in this unit and a larger M48 aperture reduces Vignetting (darkening at the field edges) when using a full size 35mm film equivalent CCD camera chip.
Spacing from rear flat shoulder of the PlanoStar to the CCD film plane is approximately 51-56mm and one can use the Altair Astro M48 variable spacer system to fine-tune the optimum distance for their particular chip and filter setup.
For use with DSLRs such as Canon EOS, the optional Starwave M48 DSLR Adapter is required for correct spacing. The Starwave M48 DSLR Adapter is available as a kit, or separately.
Why is a field flattener/reducer to take images with my Starwave refractor? All refractor lens systems exhibit some natural field curvature which, while not relevant for visual observation, can be visible in images. This field flattener/reducer screws directly into the rear focuser rotator of your Starwave 102ED or 110ED refractor, converting it into an astrograph with a flatter photographic field than the existing lens system alone. By reducing the focal length by a factor of 0.8x, you get a faster focal ratio, reducing exposure times.