The SD flattener HD kit is designed for a flat focal plane to produce crisp image of stars with the SD series of APO refractors. It consists of a high performance flattener lens and a connecing tube ring.
The SD flattener HD lens improves off-axis image quality greatly with a minimum change of the focal length. It covers a 44mm photographic field in diameter that is sufficient for the full frame DSLR cameras.
The same anti-reflection AS coatings that are used for our high-end VSD100F3.8 renowned for extremely high light transmission (99.9% per surface) are provided on each of the lens surfaces of the SD flattener HD. Also, matte-finish is elaborate to eliminate internal reflections and loss of light completely.
If combined with a Reducer HD sold optionally, the focal length will be reduced by 0.79 times (F.7.7 to F6.1) without diminishing the image circle of 44mm. A result is sharp image throughout the photographic field of view.
SD Flattener HD Kit
Use with SD81S
Use with SD103S
Use with SD115S