F/7.7 CCD Field Flattener for 160 f/7.5 StarFire EDF (160FF)

Description Designed for: 160 mm f/7.5 StarFire EDF Application: Digital imaging with CCD and DSLR cameras. Also suitable for video and 35mm film cameras. The 160 f/7.7 Prime Focus Field Flattener is made specifically for the 160 f/7.5 StarFire EDF with its 4" focuser. The effective speed of the 160EDF will be f/7.7 when this Field Flattener is used. Correction is essentially diffraction-limited over a 76 mm (3") circle, encompassing 3.5 degrees of sky. Stars will be pinpoint into the extreme corners of the field. Required for optimal performance: The distance from the field flattener to the focal plane is critical and must be maintained +/- 2.5 mm. If you remove the extension piece, the distance is 99.1 mm (3.9") from rear of housing to the focal plane; plenty of room for rotators, filter wheels, etc. The distance must be the OPTICAL distance - NOT the mechanical distance. Please be sure that you have accounted for the indexing effects of your filters, sensor cover slips and any oth