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   Celestron EdgeHD high definition optics are aplanatic, or corrected for spherical aberration. They are essentially conventional Schmidt-Cassegrain optics (spherical primary mirror, spherical secondary mirror, and full-aperture Schmidt aspheric corrector lens), but with the addition of a dual-element multicoated field flattener lens installed in their central baffle tube. The field flattener is designed to reduce off-axis coma and produce aberration-free images across a wide visual and photographic field of view.

   In addition to reduced off-axis coma, the EdgeHD optical system delivers an astrograph-quality flat focal plane across the entire field. Many optical designs that advertise themselves as “astrograph” quality actually produce their pinpoint stars across a curved focal plane. While this may be acceptable for visual observing, stars appear out of focus at the edge of the field when used with the flat rectangular imaging sensor of a DSLR digital camera or a large format CCD. The built-in field flattener of the EdgeHD optical system produces a focal plane more than three times flatter than a standard Schmidt-Cassegrain telescope and dramatically flatter than other competing coma-free designs. This guarantees visibly sharp stars across some of the largest CCD and DSLR chips available today.

   The superior edge performance of the EdgeHD optic system not only creates rounder, more point-like, and more pleasing stars at the edge of the field but actually improves the resolution and limiting magnitude when compared to telescopes of equal aperture. Poor edge quality or field curvature in conventional optics can spread out a star’s image at the edge of the field so much so that the brightness of a star appears the same as the sky background, making it undetectable to your eye (or camera). EdgeHD optics give you smaller (more concentrated) stars that create brighter images that pop out of the sky background, allowing you to see down to a fainter magnitude. This lets you capture fainter stars and galaxies out to the corners of your full frame camera chip than is possible with conventional telescope designs of equal aperture.

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