Hi Stan,

The focal reducer does just what the name implies...it reduces the focal length of the scope. Since focal ratio is focal length divided by aperture, the focal ratio is also reduced. A 'faster' focal ratio allows more light to populate a CCD chip faster than a slower f/ratio. It also means that the FOV will be wider.

As far as focusing goes, in practice it will essentially be the same. For visual use the focal reducer will give a wider field of view and flatter field...that's about it. The focal reducer is screwed on the rear of the OTA in front of the diagonal on the the SCT threads.

Patrick