The Celestron EdgeHD 17
On-axis, the spots show that the 8-inch EdgeHD is diffraction-
limited in both green (for visual observing) and red (for imaging).
And because blue rays are strongly concentrated inside the
Airy disk, the 8-inch EdgeHD is diffraction-limited in blue light.
Off-axis, its images remain diffraction-limited over a field larger
than the full Moon.
For an imager using an APS-C digital SLR camera, relative
illumination falls to 84% at the extreme corners of the image.
Although for bright subjects this minor falloff would pass
unnoticed, for imaging faint objects we recommend making and
applying flat-field images for the best results. For CCD imaging,
we always recommend making flat field images.
Portability and affordability are the hallmarks of the EdgeHD
800. Although the 8-inch covers a 42mm image circle, we
optimized its optics for the central 28mm area, the size of an
APS-C chip in many popular digital SLR cameras.
Celestron EdgeHD 800
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