Features

• An ultimate 5-group 5-element fast-ratio astrograph for both photo- and visual astronomers
• 5-group and 5-element design (two SD lenses) realizes extremely high-level correction for aberration
• Significant improvement in peripheral light intensity
• Exhibiting high performance even in visual observation from low to high magnification
• Compatible with ZWO EAF (focuser)

Description

An ultimate 5-group 5-element fast-ratio astrograph for both photo- and visual astronomers. 
The flagship model pursues maximum performance and ease of use for both astrophotography and visual observation. Uncompromising optical design gorgeously using two top grade SD and one high-refractive index ED lens in convex lens and high-quality lanthanum glass for concave lens achieved successfully much more excellent aberration correction than the conventional VSD100F3.8 ensuring extraordinary sharp, beautiful and uniform star images from the center of the field to the edge of the large format 44 x 33mm as well as the 35mm full size. As an astrograph, VSD90SS also offers excellent visual observation ranging from star observation in a wide field of view to planetary observation at high magnification.

5-group and 5-element design (two SD lenses) realizes extremely high level correction for aberration. 
Vixen VSD90SS is optically designed focusing on correction of axial chromatic aberration employing two SD and one high-refractive-index ED lenses for the convex lens and newly developed high performance lanthanum-based glass for the convex lens. In particular, the newly attempted use of two SD lenses (almost the same diameter) is a new attempt successfully suppressed at an extremely high level the deterioration in color of the star image and the distortion of the star image due to focus and squaring shifts, and both image formation and peripheral image performance exceed those of the VSD100F3.8. From shooting to image processing, you can expect consistently easy-to- use and stable shooting results.

Significant improvement in peripheral light intensity.
The helicoid focuser in the previous model VSD100F3.8 which was inherited from its parent PENTAX 100SDUFII limited the diameter of the rear lens group. In order to eliminate this restriction, the VSD90SS employed a rack and pinion focuser and increased the diameter of the rear lens group.
VSD90SS greatly improved vignetting compared to VSD100F3.8. In addition, vignetting is reduced, there is almost no vignetting due to the optical system, and non-axisymmetric flares of bright stars caused by light diffraction are also prevented. With little vignetting and plenty of peripheral illumination, it is possible to maintain abundant gradation in the periphery of the field of view, and also to facilitate peripheral illumination correction during image processing. * Depending on the shooting system, vignetting may occur due to the camera body or camera mount.

Exhibiting high performance even in visual observation from low to high magnification.
When observing at low magnification and wide field of view, the image surface is very flat, and when combined with high-quality eyepieces, a sharp image spreads over the entire field of view. Furthermore, the center of the field of view boasts a multi-wavelength Strehl intensity of 96.7%. The image formation performance exceeds 95.7% of the SD81SII, which has a reputation as a high-performance apochromat, making it also suitable for high-magnification observations of planets and other objects.

Compatible with ZWO EAF (focuser)
Compatible with dual speed focuser and ZWO EAF (focuser) (cannot be used both together).

Specs

Warranty

Vixen warranties its products to be free from initial defects in materials and workmanship for a specified period based on part type:

Vixen Electronic Parts: Limited One Year Warranty

Vixen Mechanical Parts: Limited Two Year Warranty

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