Takahashi FC-76D Flattener
This flattener from Takahashi is compatible with FC-76 and FS-78 optical tubes. This can help aid in astrophotography, specifically in deep sky because it reduces the focal ratio. When the dedicated flattener is used it changed the focal ratio to f/7.8 at 594mm when used with the FC-76S or D models. This produces a ø40mm flat field image circle. The dedicated reducer changes the focal length to 417mm and the f-stop to f/5.5. The image circle is ø36mm.