The kit consists of the high-performance flattener lens, reducer lens and connecting rings (Spacer Ring SD81, EX Tube 66) designed for prime focus astrophotography with the SD81S, SD103S and SD115S optical tubes, extraordinary enhancing the flat-field performance, while reducing the focal length by 0.79x. Enjoy high-level prime focus astrophotography by SD series optical tubes which supply two different focal length.
The SD flattener HD improves the flat-field performance toward the edge of field of view closely maintaining the original focal length of the SD-series optical tubes, fully covering the imaging field of DSLR camera with full-format sensor at image circle of 44mm diameter. Using in combination with the supplied Reducer HD, the focal length will be reduced by 0.79x (f/7.7→6.1), while maintaining image circle in dia. 44mm, largely improving sharpness over the entire imaging field of the DSLR camera with full-format sensor.
The same anti-reflective AS coating, which are used for our high-end VSD 100 f/3.8 Astrograph, are used to take advantage of 99.9% superb high transmission of light per lens surface. Loss of light, ghost and flare images are eliminated substantially due to the complete matte finish inside.
The supplied Reducer HD can be used as a reducer for the AX103S and VC200L optical tubes. The AX103S optical tube incorporates a flattener lens and outperforms high imaging capability even by itself. From this reason, the Reducer HD can be used without using the SD Flattener HD. The AX103S covers an imaging field of DSLR camera with full-format sensor with 44mm image circle.
Originally incorporating a flattener lens inside, the VC200L optical tube offers high imaging capability by itself. For this reason, the Reducer HD can be used without using the SD Flattener HD together. The VC200L delivers 36mm image circle (peripheral illumination by 60%) fully covering an imaging field of DSLR camera with APS-C sensor, and also offers comparably sharp images with the center in spite of 47% peripheral illumination at dia. 44mm image circle. It covers an imaging field of DSLR camera with image circle of dia. 28.8mm with APS-C sensor and dia. 44mm with full-format sensor.
Full-format and APS-C is a common name for size representing the size of the light-receiving plane (imaging sensor or film) of DSLR camera. Full-format (36x24mm), APS-C (23x16mm) and Four Thirds (17.3x13mm) are typical available standard for DSLR cameras. In general, the larger the light-receiving plane, the larger the range can be shot.
