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NGM 0.33X MAXfield

#17403 - NextGen MAXfield  NGM 0.33X Telecompressor Lens

The second generation NGM 0.33X MAXfield telecompressor is perfect for the SBIG ST-7 class CCD cameras with or without a color filter wheel. The NGM is especially well-suited for most C-mount cameras including the Mallincam Video CCD cameras.

Designed specially for the classic Meade and Celestron SCT's, the NGM yields an incredible f/3.3 effective focal ratio (EFL) on native f/10 systems. When used with an f/11 classic C-14, the NGM will yield an EFL of f/3.7. Results may vary slightly depending upon the imaging train configuration.  Best results will be obtained when used with the TCF-S Temperature Compensating Focuser.

User Images
Bob Benamati's NGC5907 image

Photo used with permission - Image © Bob Benamati

Bob Benamati captured this image of the edge-on galaxy NGC5907 using the NextGEN MAXfield 0.33X with a classic Celestron C-11 SCT mounted on a Losmandy G11.  A TCF-S focuser was used with the C11 to find perfect focus.



Optical Design

The optical design of the NextGEN 0.33X was performed using 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 the actual optical prescription for a SCT with the inherit aberrations of this telescope. 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:

  • Click here to see spot diagram
  • Click here to see encircled energy diagram
  • Click here to see ray trace diagram
  • Click here to see field curvature diagram

Telescope-Side Compatibility:

  • TCF-S focuser,
  • Any 2-inch focuser or receiver.

Camera-Side Compatibility:

  • NextGEN Camera-specific mount.  See this table for currently supported cameras.
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Additional Information:

Historical Perspective

The original 0.33X Maxfield was first introduced many years ago and was designed for cameras such as the ST-6 and 7 with CCDs deficient in blue sensitivity. The design wavelengths were 500, 650 and 850 nm and was not really intended for RGB imaging which was in its infancy. You can still see on the web a report comparing the old MAXfield to the Meade telecompressor here. While the reviewer gave the Meade a slight edge over the Optec unit primarily because of cost, it is important to note that the NGM is now priced competitive to the Meade unit and has been completely redesigned to perform better optically. The same quality mechanical mounting noted in the review has not changed.