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NextGEN Ultra WideField 0.7XL

#17409 - NextGen Ultra WideField NGUW 0.50X Telecompressor Lens

The Ultra WideField 0.7XL is a coupler from Optec and is designed specifically to speed up the focal ratios of highly corrected telescope systems. This design assumes that the image formed by the telescope is reasonably flat and aberration free. If so, the resulting image will also be highly corrected and nearly parfocal with the original image. Optimized for an f/8, the Ultra WideField 0.7XL will work for any focal ratio in the range of f/5.6 to f/20. The field is highly corrected up to 18mm in diameter and would work well even with larger fields with only slight degradation near the corners.

Like the other reducers in the NextGEN series, all surfaces have a broadband multilayer coating optimized for the 450 - 650 nm pass band of the optic. Filter mounted in front as with the IFW are compatible. In fast systems, it is always better optically to mount the filters in front of any reducer optic to keep the incoming rays closer to being normal (collimated) to the filter surface.

The Ultra WideField 0.7XL was redesigned and improved in late 2006 and now has a much longer back-focus distance and uses the same mounting plate adapters as the 0.33X and 0.50X models. This allows use of this reducer with SBIG cameras having the CFW-8/10 filter wheels mounted.

User Images
David Haworth's IC5070

Photo used with permission - Image © David Haworth

David Haworth's beautiful image of the Pelican Nebula was captured using the NextGEN Ultra WideField 0.7XL telecompressor on a Pentax 75mm SDHF APO refractor. This image was taken with a QSI 520 CCD camera and is the result of over 3 hours of exposure time.

Optical Design

The optical design of the NextGEN  0.7XL was done with Zemax and optimized for four field points using wavelengths of 450, 550 and 650 nm. The goal was for the smallest blur diameters for the four field points. The system was modeled using an idealized telescope of f/8 and with perfect optics. The resulting lens curvatures of this designed were made without adjusting the radii to the optical lab's tool list. Custom tools were made for all surfaces. The Zemax results are shown below:

Telescope-Side Compatibility:

Camera-Side Compatibility:

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