Field Flattener For f/5 to f/7 Refractors

This is a field flattener for refractor-type telescopes with a focal ratio of f/5 to f/7 Causes no change to the telescope focal length 2-inch barrel to easily attach to a two-inch focuser Fully multi-coated optics T-ring thread on the device so a T-ring can be used to easily attach a DSLR camera or a dedicated astrocamera 38 mm of clear aperture Requires 55mm (+/-2) of back focus/spacing between the device and the camera sensor Premium high glossy anodizing finish When doing astrophotography with refractor-type telescopes, the faster the focal ratio the more field curvature becomes a problem. Field curvature will appear in the corners of astrophotographs, making the stars smear perpendicular to the axis of the image. This is called coma -- coma is Latin for comet, because the stars look like comets. The more the curvature, the closer to the center the coma appears. The larger the sensor, the worse the coma. Astrophotographers can easily correct the coma by using a field flattener – an optical device that goes between the telescope and the camera. Field fatteners are not interchangeable, because these devices are designed to work with a small range of focal ratios. The Explore Scientific field flattener is designed to work with telescopes with focal ratios between f/5 and f/7. Our device requires 55 mm (+/-2 mm) of spacing between the back of the device and the camera sensor. Fits the following Explore Scientific telescopes: DAR1020765-01 DAR127065-02 DAR152065-01 ES-ED0806-02 ES-ED10207-02 FCD100-0806-01 FCD100-10207-02